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Sample records for cumn spin glass

  1. Spin glasses

    CERN Document Server

    Bovier, Anton

    2007-01-01

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

  2. Spin glass transition in canonical AuFe alloys: A numerical study

    Science.gov (United States)

    Zhang, Kai-Cheng; Li, Yong-Feng; Liu, Gui-Bin; Zhu, Yan

    2012-05-01

    Although spin glass transitions have long been observed in diluted magnetic alloys, e.g. AuFe and CuMn alloys, previous numerical studies are not completely consistent with the experiment results. The abnormal critical exponents of the alloys remain still puzzling. By employing parallel tempering algorithm with finite-size scaling analysis, we investigated the phase transitions in canonical AuFe alloys. Our results strongly support that spin glass transitions occur at finite temperatures in the alloys. The calculated critical exponents agree well with those obtained from experiments.

  3. Spin polarization and exchange coupling of Cu and Mn atoms in paramagnetic CuMn diluted alloys induced by a Co layer

    Science.gov (United States)

    Abes, M.; Atkinson, D.; Tanner, B. K.; Charlton, T. R.; Langridge, Sean; Hase, T. P. A.; Ali, M.; Marrows, C. H.; Hickey, B. J.; Neudert, A.; Hicken, R. J.; Arena, D.; Wilkins, S. B.; Mirone, A.; Lebègue, S.

    2010-11-01

    Using the surface, interface, and element specificity of x-ray resonant magnetic scattering in combination with x-ray magnetic circular dichroism, we have spatially resolved the magnetic spin polarization, and the associated interface proximity effect, in a Mn-based high-susceptibility material close to a ferromagnetic Co layer. We have measured the magnetic polarization of Mn and Cu3d electrons in paramagnetic CuMn alloy layers in [Co/Cu(x)/CuMn/Cu(x)]20 multilayer samples with varying copper layer thicknesses from x=0 to 25Å . The size of the Mn and CuL2,3 edge dichroism shows a decrease in the Mn-induced polarization for increasing copper thickness indicating the dominant interfacial nature of the Cu and Mn spin polarization. The Mn polarization is much higher than that of Cu. Evidently, the Mn moment is a useful probe of the local spin density. Mn atoms appear to be coupled antiferromagnetically with the Co layer below x=10Å and ferromagnetically coupled above. In contrast, the interfacial Cu atoms remain ferromagnetically aligned to the Co layer for all thicknesses studied.

  4. Glassy dynamics in CuMn thin-film multilayers

    Science.gov (United States)

    Zhai, Qiang; Harrison, David C.; Tennant, Daniel; Dalhberg, E. Dan; Kenning, Gregory G.; Orbach, Raymond L.

    2017-02-01

    Thin-film multilayered spin-glass CuMn/Cu structures display glassy dynamics. The freezing temperature Tf was measured for 40 layers of CuMn films of thickness L =4.5 ,9.0 , and 20.0 nm, sandwiched between nonmagnetic Cu layers of thickness ≈60 nm. The Kenning effect, Tf∝lnL , is shown to follow from power-law dynamics where the correlation length grows from nucleation as ξ (t ,T ) =c1a0(t/τ0) c2(T /Tg) , leading to [(Tf/Tg) c2ln(tco/τ0) ] +lnc1=ln(L /a0) . Here, Tg is the bulk spin-glass temperature, c1 and c2 are constants determined from the spin-glass dynamics, tco is the time for the correlation length to grow to the film thickness, τ0 is a characteristic exchange time ≈ℏ /kBTg , and a0 is the average Mn-Mn separation. For t ≥tco , the magnetization dynamics are simple activated, with a single activation energy Δmax(L ) /kBTg=(1 /c2) [ln(L /a0) -lnc1] that does not change with time. Values for all these parameters are found for the three values of L explored in these measurements. We find experimentally Δmax(L ) /kB =907 , 1246, and 1650 K, respectively, for the three CuMn thin-film multilayer thicknesses, consistent with power-law dynamics. We perform a similar analysis based on the activated dynamics of the droplet model and find a much larger spread for Δmax(L ) than found experimentally.

  5. Perspectives on spin glasses

    CERN Document Server

    Contucci, Pierluigi

    2013-01-01

    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.

  6. Supersymmetric Spin Glass

    CERN Document Server

    Gukov, S G

    1997-01-01

    The evidently supersymmetric four-dimensional Wess-Zumino model with quenched disorder is considered at the one-loop level. The infrared fixed points of a beta-function form the moduli space $M = RP^2$ where two types of phases were found: with and without replica symmetry. While the former phase possesses only a trivial fixed point, this point become unstable in the latter phase which may be interpreted as a spin glass phase.

  7. Spin glasses on thin graphs

    CERN Document Server

    Baillie, C F; Johnston, D A; Plechác, P

    1995-01-01

    In a recent paper we found strong evidence from simulations that the Ising antiferromagnet on ``thin'' random graphs - Feynman diagrams - displayed a mean-field spin glass transition. The intrinsic interest of considering such random graphs is that they give mean field results without long range interactions or the drawbacks, arising from boundary problems, of the Bethe lattice. In this paper we reprise the saddle point calculations for the Ising and Potts ferromagnet, antiferromagnet and spin glass on Feynman diagrams. We use standard results from bifurcation theory that enable us to treat an arbitrary number of replicas and any quenched bond distribution. We note the agreement between the ferromagnetic and spin glass transition temperatures thus calculated and those derived by analogy with the Bethe lattice, or in previous replica calculations. We then investigate numerically spin glasses with a plus or minus J bond distribution fo rthe Ising and Q=3,3,10,50 state Potts models, paying particular attention t...

  8. Random Fields and Spin Glasses

    Science.gov (United States)

    De Dominicis, Cirano; Giardina, Irene

    2010-06-01

    1. A brief introduction; 2. The Random Field Ising model; 3. The dynamical approach; 4. The p=2 spherical model; 5. Mean field spin glasses: one-step RSB; 6. The Sherrington-Kirkpatrick model; 7. Mean field via TAP equations; 8. Spin glass above D=6; 9. Propagators, mostly replicon; 10. Ward-Takahashi identities and Goldstone modes; 11. Alternative approaches and conclusions; Appendices; Index.

  9. Some recent developments in spin glasses

    Indian Academy of Sciences (India)

    A P Young

    2005-06-01

    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 spins and chiralities shows that there is a single, finite-temperature transition at which both spins and chiralities order.

  10. Spin glasses and neural networks

    Energy Technology Data Exchange (ETDEWEB)

    Parga, N. (Comision Nacional de Energia Atomica, San Carlos de Bariloche (Argentina). Centro Atomico Bariloche; Universidad Nacional de Cuyo, San Carlos de Bariloche (Argentina). Inst. Balseiro)

    1989-07-01

    The mean-field theory of spin glass models has been used as a prototype of systems with frustration and disorder. One of the most interesting related systems are models of associative memories. In these lectures we review the main concepts developed to solve the Sherrington-Kirkpatrick model and its application to neural networks. (orig.).

  11. Spin anisotropy and slow dynamics in spin glasses.

    Science.gov (United States)

    Bert, F; Dupuis, V; Vincent, E; Hammann, J; Bouchaud, J-P

    2004-04-23

    We report on an extensive study of the influence of spin anisotropy on spin glass aging dynamics. New temperature cycle experiments allow us to compare quantitatively the memory effect in four Heisenberg spin glasses with various degrees of random anisotropy and one Ising spin glass. The sharpness of the memory effect appears to decrease continuously with the spin anisotropy. Besides, the spin glass coherence length is determined by magnetic field change experiments for the first time in the Ising sample. For three representative samples, from Heisenberg to Ising spin glasses, we can consistently account for both sets of experiments (temperature cycle and magnetic field change) using a single expression for the growth of the coherence length with time.

  12. Equilibrium avalanches in spin glasses

    Science.gov (United States)

    Le Doussal, Pierre; Müller, Markus; Wiese, Kay Jörg

    2012-06-01

    We study the distribution of equilibrium avalanches (shocks) in Ising spin glasses which occur at zero temperature upon small changes in the magnetic field. For the infinite-range Sherrington-Kirkpatrick (SK) model, we present a detailed derivation of the density ρ(ΔM) of the magnetization jumps ΔM. It is obtained by introducing a multicomponent generalization of the Parisi-Duplantier equation, which allows us to compute all cumulants of the magnetization. We find that ρ(ΔM)˜ΔM-τ with an avalanche exponent τ=1 for the SK model, originating from the marginal stability (criticality) of the model. It holds for jumps of size 1≪ΔMmodel. For finite-range models, using droplet arguments, we obtain the prediction τ=(df+θ)/dm where df,dm, and θ are the fractal dimension, magnetization exponent, and energy exponent of a droplet, respectively. This formula is expected to apply to other glassy disordered systems, such as the random-field model and pinned interfaces. We make suggestions for further numerical investigations, as well as experimental studies of the Barkhausen noise in spin glasses.

  13. Novel spin glasses by mechanical milling

    Institute of Scientific and Technical Information of China (English)

    周国富; H.Bakker

    1996-01-01

    Novel spin-glass alloys were synthesized by milling intermetallic compounds and also by milling mixtures of crystalline elemental powder in a high-energy ball mill.Spin glass behaviour was found in amorphous Co2Ge,which was amorphised by milling in mechanically disordered crystalline GdAl2 in ball-milled crystalline and amorphous CoZr,and in mechanically alloyed Co-Cu,which formed a supersaturated f.c.c.solid solution.All these materials are binary alloys and tlie concentration of the magnetic element is high,which makes them novel types of spin glasses.It is shown that ball milling may not only lead to structural metallic glasses,but can also generate the magnetic pendant of a structural glass,namely the spin glass.

  14. Spin-glass transition of the three-dimensional Heisenberg spin glass.

    Science.gov (United States)

    Campos, I; Cotallo-Aban, M; Martin-Mayor, V; Perez-Gaviro, S; Tarancon, A

    2006-11-24

    It is shown, by means of Monte Carlo simulation and finite size scaling analysis, that the Heisenberg spin glass undergoes a finite-temperature phase transition in three dimensions. There is a single critical temperature, at which both a spin glass and a chiral glass ordering develop. The Monte Carlo algorithm, adapted from lattice gauge theory simulations, makes it possible to thermalize lattices of size L = 32, larger than in any previous spin-glass simulation in three dimensions. High accuracy is reached thanks to the use of the Marenostrum supercomputer. The large range of system sizes studied allows us to consider scaling corrections.

  15. Antibacterial properties of laser spinning glass nanofibers.

    Science.gov (United States)

    Echezarreta-López, M M; De Miguel, T; Quintero, F; Pou, J; Landin, M

    2014-12-30

    A laser-spinning technique has been used to produce amorphous, dense and flexible glass nanofibers of two different compositions with potential utility as reinforcement materials in composites, fillers in bone defects or scaffolds (3D structures) for tissue engineering. Morphological and microstructural analyses have been carried out using SEM-EDX, ATR-FTIR and TEM. Bioactivity studies allow the nanofibers with high proportion in SiO2 (S18/12) to be classified as a bioinert glass and the nanofibers with high proportion of calcium (ICIE16) as a bioactive glass. The cell viability tests (MTT) show high biocompatibility of the laser spinning glass nanofibers. Results from the antibacterial activity study carried out using dynamic conditions revealed that the bioactive glass nanofibers show a dose-dependent bactericidal effect on Sthaphylococcus aureus (S. aureus) while the bioinert glass nanofibers show a bacteriostatic effect also dose-dependent. The antibacterial activity has been related to the release of alkaline ions, the increase of pH of the medium and also the formation of needle-like aggregates of calcium phosphate at the surface of the bioactive glass nanofibers which act as a physical mechanism against bacteria. The antibacterial properties give an additional value to the laser-spinning glass nanofibers for different biomedical applications, such as treating or preventing surgery-associated infections. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Energy gap in concentrated spin glasses

    Energy Technology Data Exchange (ETDEWEB)

    Liao, S.B.; Bhagat, S.M.; Manheimer, M.A.; Moorjani, K.

    1988-04-15

    Using magnetic resonance data at several frequencies, we have obtained the temperature dependence of the field-induced magnetization (M) in three concentrated spin glasses. At every frequency, M is independent of T for Tapprox. spin-glass transition temperatures T/sub SG/.

  17. Interface energies in ising spin glasses.

    Science.gov (United States)

    Aspelmeier, T; Moore, M A; Young, A P

    2003-03-28

    The replica method has been used to calculate the interface free energy associated with the change from periodic to antiperiodic boundary conditions in finite-dimensional spin glasses. At mean-field level the interface free energy vanishes, but after allowing for fluctuation effects, a nonzero interface free energy is obtained which is significantly different from numerical expectations.

  18. Chiral-glass transition and replica symmetry breaking of a three-dimensional heisenberg spin glass

    Science.gov (United States)

    Hukushima; Kawamura

    2000-02-01

    Extensive equilibrium Monte Carlo simulations are performed for a three-dimensional Heisenberg spin glass with the nearest-neighbor Gaussian coupling to investigate its spin-glass and chiral-glass orderings. The occurrence of a finite-temperature chiral-glass transition without the conventional spin-glass order is established. Critical exponents characterizing the transition are different from those of the standard Ising spin glass. The calculated overlap distribution suggests the appearance of a peculiar type of replica-symmetry breaking in the chiral-glass ordered state.

  19. Replica symmetric spin glass field theory

    Energy Technology Data Exchange (ETDEWEB)

    Temesvari, T. [Research Group for Theoretical Physics of the Hungarian Academy of Sciences, Eoetvoes University, Pazmany Peter setany 1/A, H-1117 Budapest (Hungary)]. E-mail: temtam@helios.elte.hu

    2007-06-18

    A new powerful method to test the stability of the replica symmetric spin glass phase is proposed by introducing a replicon generator function g(v). Exact symmetry arguments are used to prove that its extremum is proportional to the inverse spin glass susceptibility. By the idea of independent droplet excitations a scaling form for g(v) can be derived, whereas it can be exactly computed in the mean field Sherrington-Kirkpatrick model. It is shown by a first order perturbative treatment that the replica symmetric phase is unstable down to dimensions d < or approx. 6, and the mean field scaling function proves to be very robust. Although replica symmetry breaking is escalating for decreasing dimensionality, a mechanism caused by the infrared divergent replicon propagator may destroy the mean field picture at some low enough dimension.

  20. Replica symmetric spin glass field theory

    Science.gov (United States)

    Temesvári, T.

    2007-06-01

    A new powerful method to test the stability of the replica symmetric spin glass phase is proposed by introducing a replicon generator function g(v). Exact symmetry arguments are used to prove that its extremum is proportional to the inverse spin glass susceptibility. By the idea of independent droplet excitations a scaling form for g(v) can be derived, whereas it can be exactly computed in the mean field Sherrington-Kirkpatrick model. It is shown by a first order perturbative treatment that the replica symmetric phase is unstable down to dimensions d≲6, and the mean field scaling function proves to be very robust. Although replica symmetry breaking is escalating for decreasing dimensionality, a mechanism caused by the infrared divergent replicon propagator may destroy the mean field picture at some low enough dimension.

  1. From random walks to spin glasses

    Science.gov (United States)

    Derrida, B.

    1997-02-01

    The talk was a short review on systems which exhibit non-self-averaging effects: sums of random variables when the distribution has a long tail, mean field spin glasses, random map models and returns of a random walk to the origin. Non-self-averaging effects are identical in the case of sums of random variables and in the spin glass problem as predicted by the replica approach. Also we will see that for the random map models or for the problem of the returns of a random walk to the origin, the non-self-averaging effects coincide with the results of the replica approach when the number n of replica n = - {1}/{2} or n = -1.

  2. Mean field models for spin glasses

    CERN Document Server

    Talagrand, Michel

    2011-01-01

    This is a new, completely revised, updated and enlarged edition of the author's Ergebnisse vol. 46: "Spin Glasses: A Challenge for Mathematicians". This new edition will appear in two volumes, the present first volume presents the basic results and methods, the second volume is expected to appear in 2011. In the eighties, a group of theoretical physicists introduced several models for certain disordered systems, called "spin glasses". These models are simple and rather canonical random structures, of considerable interest for several branches of science (statistical physics, neural networks and computer science). The physicists studied them by non-rigorous methods and predicted spectacular behaviors. This book introduces in a rigorous manner this exciting new area to the mathematically minded reader. It requires no knowledge whatsoever of any physics. The first volume of this new and completely rewritten edition presents six fundamental models and the basic techniques to study them.

  3. Universality in bipartite mean field spin glasses

    CERN Document Server

    Genovese, Giuseppe

    2011-01-01

    In this work we give a proof of full universality with respect to the choice of the statistical distribution of the quenched noise, for many models of bipartite spin glasses. By using Guerra's interpolation tecnique we estimate the difference between the free energy of the gaussian model and the ones derived by a general class of random interactions, and check how it vanishes in the thermodynamic limit.

  4. Literature Review of Spin On Glass

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, Reuben James [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-03-02

    Spin on glass (SOG) is a promising material that combines the planarization properties of a low-viscosity liquid with a dielectric constant lower than that of silicon dioxide. However, as this paper will show, this material comes with significant processing and material properties challenges that must be understood and overcome. Significant research has been accomplished through a variety of processing techniques that will be reviewed here.

  5. Spin Glasses : Statics and Dynamics : Summer School

    CERN Document Server

    Bovier, Anton

    2009-01-01

    Over the last decade, spin glass theory has turned from a fascinating part of t- oretical physics to a ?ourishing and rapidly growing subject of probability theory as well. These developments have been triggered to a large part by the mathem- ical understanding gained on the fascinating and previously mysterious “Parisi solution” of the Sherrington–Kirkpatrick mean ?eld model of spin glasses, due to the work of Guerra, Talagrand, and others. At the same time, new aspects and applications of the methods developed there have come up. The presentvolumecollects a number of reviewsaswellas shorterarticlesby lecturers at a summer school on spin glasses that was held in July 2007 in Paris. These articles range from pedagogical introductions to state of the art papers, covering the latest developments. In their whole, they give a nice overview on the current state of the ?eld from the mathematical side. The review by Bovier and Kurkova gives a concise introduction to mean ?eld models, starting with the Curie–...

  6. Numerical evidence of spin-chirality decoupling in the three-dimensional heisenberg spin glass model.

    Science.gov (United States)

    Viet, Dao Xuan; Kawamura, Hikaru

    2009-01-16

    Ordering of the three-dimensional Heisenberg spin glass with Gaussian coupling is studied by extensive Monte Carlo simulations. The model undergoes successive chiral-glass and spin-glass transitions at nonzero temperatures T_{CG}>T_{SG}>0, exhibiting spin-chirality decoupling.

  7. PREFACE: Viewing the World through Spin Glasses

    Science.gov (United States)

    Coolen, Ton; Nishimori, Hidetoshi; Sourlas, Nicolas; Wong, Michael

    2008-08-01

    This special issue of Journal of Physics A: Mathematical and Theoretical collects papers by speakers and participants of the conference `Viewing the World through Spin Glasses', held in Oxford (UK) on 31 August and 1 September 2007 in honour of Professor David Sherrington. It also includes contributions by many other active researchers in the field of spin glasses and related problems. The theory of spin glasses has a history of more than 30 years and continues to develop within itself as well as into an unexpectedly vast range of interdisciplinary subjects, including neural networks, error-correcting codes, optimization problems and social problems. Most of these amazing developments have their formal basis in the ground-breaking work of David Sherrington with Scott Kirkpatrick, centred on the SK model and the techniques devised to analyse it via the replica method. In this 'classic-of-classics' paper, a theoretical paradigm was suddenly established which became the common tool of analysis for thousands of papers in the following decades. It also led to deep developments in probability theory, through the efforts to understand the enigmatic Parisi solution of the SK model. The work of Professor Sherrington will continue to be an infinite source of our inspiration in many years to come. The purpose of the conference `Viewing the World through Spin Glasses' was to provide an overview of the present status of the fields which Professor Sherrington initiated, on the occasion of his 65th birthday, organized by John Cardy, Juan P Garrahan and the present Guest Editors. The first contribution in this special issue, by Professor Paul Goldbart, reflects his salute delivered at the conference dinner, and conveys its atmosphere very well. The papers that follow, ordered by the date of acceptance, represent the current activities of leading researchers in spin glasses and related fields, and we expect these to serve as milestones for future developments. We thank all the

  8. Quantum Optimization of Fully Connected Spin Glasses

    Science.gov (United States)

    Venturelli, Davide; Mandrà, Salvatore; Knysh, Sergey; O'Gorman, Bryan; Biswas, Rupak; Smelyanskiy, Vadim

    2015-07-01

    Many NP-hard problems can be seen as the task of finding a ground state of a disordered highly connected Ising spin glass. If solutions are sought by means of quantum annealing, it is often necessary to represent those graphs in the annealer's hardware by means of the graph-minor embedding technique, generating a final Hamiltonian consisting of coupled chains of ferromagnetically bound spins, whose binding energy is a free parameter. In order to investigate the effect of embedding on problems of interest, the fully connected Sherrington-Kirkpatrick model with random ±1 couplings is programmed on the D-Wave TwoTM annealer using up to 270 qubits interacting on a Chimera-type graph. We present the best embedding prescriptions for encoding the Sherrington-Kirkpatrick problem in the Chimera graph. The results indicate that the optimal choice of embedding parameters could be associated with the emergence of the spin-glass phase of the embedded problem, whose presence was previously uncertain. This optimal parameter setting allows the performance of the quantum annealer to compete with (and potentially outperform, in the absence of analog control errors) optimized simulated annealing algorithms.

  9. Quantum Optimization of Fully Connected Spin Glasses

    Directory of Open Access Journals (Sweden)

    Davide Venturelli

    2015-09-01

    Full Text Available Many NP-hard problems can be seen as the task of finding a ground state of a disordered highly connected Ising spin glass. If solutions are sought by means of quantum annealing, it is often necessary to represent those graphs in the annealer’s hardware by means of the graph-minor embedding technique, generating a final Hamiltonian consisting of coupled chains of ferromagnetically bound spins, whose binding energy is a free parameter. In order to investigate the effect of embedding on problems of interest, the fully connected Sherrington-Kirkpatrick model with random ±1 couplings is programmed on the D-Wave Two^{TM} annealer using up to 270 qubits interacting on a Chimera-type graph. We present the best embedding prescriptions for encoding the Sherrington-Kirkpatrick problem in the Chimera graph. The results indicate that the optimal choice of embedding parameters could be associated with the emergence of the spin-glass phase of the embedded problem, whose presence was previously uncertain. This optimal parameter setting allows the performance of the quantum annealer to compete with (and potentially outperform, in the absence of analog control errors optimized simulated annealing algorithms.

  10. Fluctuation-dissipation ratio of the Heisenberg spin glass.

    Science.gov (United States)

    Kawamura, Hikaru

    2003-06-13

    The fluctuation-dissipation (FD) relation of the three-dimensional Heisenberg spin glass with weak random anisotropy is studied by off-equilibrium Monte Carlo simulation. The numerically determined FD ratio exhibits a "one-step-like" behavior, the effective temperature of the spin-glass state being about twice the spin-glass transition temperature, T(eff) approximately 2T(g), irrespective of the bath temperature. The results are discussed in conjunction with the recent experiment by Hérisson and Ocio, and with the chirality scenario of the spin-glass transition.

  11. Aging, rejuvenation and memory phenomena in spin glasses

    Indian Academy of Sciences (India)

    V Dupuis; F Bert; J-P Bouchaud; J Hammann; F Ladieu; D Parker; E Vincent

    2005-06-01

    In this paper, we review several important features of the out-of-equilibrium dynamics of spin glasses. Starting with the simplest experiments, we discuss the scaling laws used to describe the isothermal aging observed in spin glasses after a quench down to the low-temperature phase. We report in particular new results on the sub-aging behaviour of spin glasses. We then discuss the rejuvenation and memory effects observed when a spin glass is submitted to temperature variations during aging, from the point of view of both energy landscape pictures and real-space pictures. We highlight the fact that both approaches point out the necessity of hierarchical processes involved in aging. Finally, we report an investigation of the effect of small temperature variations on aging in spin glass samples with various anisotropies which indicates that this hierarchy depends on the spin anisotropy.

  12. Spin- and Pair-Density-Wave Glasses

    Directory of Open Access Journals (Sweden)

    David F. Mross

    2015-07-01

    Full Text Available Spontaneous breaking of translational symmetry, known as density-wave order, is common in nature. However, such states are strongly sensitive to impurities or other forms of frozen disorder leading to fascinating glassy phenomena. We analyze impurity effects on a particularly ubiquitous form of broken translation symmetry in solids: a spin-density wave (SDW with spatially modulated magnetic order. Related phenomena occur in pair-density-wave (PDW superconductors where the superconducting order is spatially modulated. For weak disorder, we find that the SDW or PDW order can generically give way to a SDW or PDW glass—new phases of matter with a number of striking properties, which we introduce and characterize here. In particular, they exhibit an interesting combination of conventional (symmetry-breaking and spin-glass (Edwards-Anderson order. This is reflected in the dynamic response of such a system, which—as expected for a glass—is extremely slow in certain variables, but, surprisingly, is fast in others. Our results apply to all uniaxial metallic SDW systems where the ordering vector is incommensurate with the crystalline lattice. In addition, the possibility of a PDW glass has important consequences for some recent theoretical and experimental work on La_{2−x}Ba_{x}Cu_{2}O_{4}.

  13. Practical engineering of spin-glass instances

    CERN Document Server

    Marshall, Jeffrey; Hen, Itay

    2016-01-01

    Recent technological developments in the field of experimental quantum annealing have made prototypical annealing optimizers with hundreds of qubits commercially available. The experimental demonstration of a quantum speedup for optimization problems has since then become a coveted, albeit elusive goal. Recent studies have shown that the so far inconclusive results as to the appearance of such quantum enhancements, may have been partly due to the benchmark problems used being unsuitable, allowing for both traditional resources and quantum annealers to solve them with no special efforts. The need therefore has arisen for the generation of harder benchmarks which would hopefully possess the discriminative power to separate classical scaling of performance with size, from quantum. We introduce here a practical technique for the engineering of extremely hard spin glass Ising-type problem instances that does not require `cherry picking' from large ensembles of randomly generated instances. We accomplish this by tr...

  14. Infinite-Range Quantum Dzyaloshinskii-Moriya Spin Glass Model

    Institute of Scientific and Technical Information of China (English)

    商育民; 姚凯伦

    2003-01-01

    Based on the replica method and the imaginary time functional-integral technique,we investigate the infiniterange quantum Dzyaloshinskii-Moriya spin glass model.It is found that the quantum Dzyaloshinskii-Moriya spin glass model behaves in a Heisenberg-like manner.The specific heat has the crossover behaviour.The broad Maximum in specific heat is shifted to higher temperature with increasing applied field.These features are in good agreement with the observation of Brodale et al.[J.Magn.Magn.Matter.31-34(1983)1331] The susceptibility of the system has the typical spin glass feature.

  15. CONSEQUENCES OF COLE-COLE RELAXATION IN SPIN GLASSES

    OpenAIRE

    Baalbergen, J.; Ong, T; Van Duyneveldt, A.; Verstelle, J.

    1988-01-01

    Ac susceptibility measurements in spin glasses over an extended frequency range indicate a Cole-Cole behaviour at temperatures from well above to far below the freezing temperature. The consequences of this kind of relaxation are discussed.

  16. Frustration in Vicinity of Transition Point of Ising Spin Glasses

    Science.gov (United States)

    Miyazaki, Ryoji

    2013-09-01

    We conjecture the existence of a relationship between frustration and the transition point at zero temperature of Ising spin glasses. The relation reveals that, in several Ising spin glass models, the concentration of ferromagnetic bonds is close to the critical concentration at zero temperature when the output of a function about frustration is equal to unity. The function is the derivative of the average number of frustrated plaquettes with respect to the average number of antiferromagnetic bonds. This relation is conjectured in Ising spin glasses with binary couplings on two-dimensional lattices, hierarchical lattices, and three-body Ising spin glasses with binary couplings on two-dimensional lattices. In addition, the same argument in the Sherrington--Kirkpatrick model yields a point that is identical to the replica-symmetric solution of the transition point at zero temperature.

  17. Hierarchical models and chaotic spin glasses

    Science.gov (United States)

    Berker, A. Nihat; McKay, Susan R.

    1984-09-01

    Renormalization-group studies in position space have led to the discovery of hierarchical models which are exactly solvable, exhibiting nonclassical critical behavior at finite temperature. Position-space renormalization-group approximations that had been widely and successfully used are in fact alternatively applicable as exact solutions of hierarchical models, this realizability guaranteeing important physical requirements. For example, a hierarchized version of the Sierpiriski gasket is presented, corresponding to a renormalization-group approximation which has quantitatively yielded the multicritical phase diagrams of submonolayers on graphite. Hierarchical models are now being studied directly as a testing ground for new concepts. For example, with the introduction of frustration, chaotic renormalization-group trajectories were obtained for the first time. Thus, strong and weak correlations are randomly intermingled at successive length scales, and a new microscopic picture and mechanism for a spin glass emerges. An upper critical dimension occurs via a boundary crisis mechanism in cluster-hierarchical variants developed to have well-behaved susceptibilities.

  18. Finite block pseudo-spin approach of proton glass

    Science.gov (United States)

    Lee, Kwang-Sei; Koo, Je Huan; Lee, Cheol Eui

    2016-08-01

    We herein propose an alternative phenomenology to explain the phase of proton glass by reference to finite block spin theory in magnetism, in which the phase may be considered as being a short-range ferroelectric ordering of block pseudo-spins comprised of random pseudo-spins that have a majority of individual pseudo-spins in a given sense. By making use of the Curie law of block pseudo-spins, we obtained the dielectric susceptibility for the lower and higher temperature approximations of the Brillouin function. The experimental results for the susceptibility in hydrogen-bonded mixed crystals of ferroelectric RbH2P(As)O4 and antiferroelectric NH4H2P(As)O4 were thus fitted fairly well at low temperatures in the proton glass phase whereas some deviation from our formulation was seen at high temperatures in the paraelectric phase.

  19. Magnetoelectric Coupling Induced Electric Dipole Glass State in Heisenberg Spin Glass

    Institute of Scientific and Technical Information of China (English)

    LIU Jun-Ming; CHAN-WONG Lai-Wa; CHOY Chung-Loong

    2009-01-01

    Multiferroic behavior in an isotropic Heisenberg spin glass with Gaussian random fields,incorporated bymagnetoelectric coupling derived from the Landau symmetry argument,are investigated.Electric dipole glass transitions at finite ternperature,due to coupling,are demonstrated by Monte Carlo simulation.This electric dipole glass state is solely ascribed to the coupling term with chiral symmetry of the magnetization,while the term associated with the spatial derivative of the squared magnetization has no contribution.

  20. Nonequilibrium spin glass dynamics with the Janus computer

    Science.gov (United States)

    Yllanes, David; Belletti, F.; Cruz, A.; Fernandez, L. A.; Gordillo-Guerrero, A.; Guidetti, M.; Maiorano, A.; Mantovani, F.; Marinari, E.; Martin-Mayor, V.; Monforte, J.; Munoz Sudupe, A.; Navarro, D.; Parisi, G.; Perez-Gaviro, S.; Ruiz-Lorenzo, J. J.; Schifano, S. F.; Sciretti, D.; Tarancon, A.; Tripiccione, R.

    2009-03-01

    The out of equilibrium evolution of the Edwards-Anderson spin glass is followed for a tenth of a second, effectively halving the (logarithmic) temporal gap between previous simulations and experiments. In fact, we have been able to make safe predictions about the behavior at experimental times, using mild extrapolations. This work has been made possible by Janus, a special purpose computer designed by our collaboration. We have thoroughly studied the spin glass correlation functions and the growth of the coherence length for L 0 lattices in 3D,using L 4,40 lattices to check for finite size effects. We present clear evidence for a replicon correlator. Our main conclusion is that these spin glasses follow non-coarsening dynamics, at least up to the experimentally relevant time scales.

  1. The Spin Glass-Kondo Competition in Disordered Cerium Systems

    Science.gov (United States)

    Magalhaes, S. G.; Zimmer, F.; Coqblin, B.

    2013-10-01

    We discuss the competition between the Kondo effect, the spin glass state and a magnetic order observed in disordered Cerium systems. We present firstly the experimental situation of disordered alloys such as CeNi1 - xCux and then the different theoretical approaches based on the Kondo lattice model, with different descriptions of the intersite exchange interaction for the spin glass. After the gaussian approach of the Sherrington-Kirkpatrick model, we discuss the Mattis and the van Hemmen models. Then, we present simple cluster calculations in order to describe the percolative evolution of the clusters from the cluster spin glass to the inhomogeneous ferromagnetic order recently observed in CeNi1 - xCux disordered alloys and finally we discuss the effect of random and transverse magnetic field.

  2. Metastable states of a spin glass chain at 0 temperature

    Energy Technology Data Exchange (ETDEWEB)

    Derrida, B.; Gardner, E.

    1986-06-01

    We consider an Ising spin glass chain at 0 temperature. The moments of the total number of metastable states and the typical number of metastable states at a given magnetization are calculated. We find that for all magnetizations less than or equal to msub(max)=0.446042... there is an exponentially large number of metastable states. For magnetizations larger than msub(max), there are no metastable states. The remanent magnetization msub(rem) is known to be 1/3 for single spin flip dynamics when one starts at time t = 0 with all the spins aligned. This shows that the remanent magnetization is not given by the metastable states of maximum magnetization. Our results are valid for a spin glass chain with an arbitrary symmetric and continuous distribution of nearest neighbour interactions.

  3. Cumulative overlap distribution function in realistic spin glasses

    Science.gov (United States)

    Billoire, A.; Maiorano, A.; Marinari, E.; Martin-Mayor, V.; Yllanes, D.

    2014-09-01

    We use a sample-dependent analysis, based on medians and quantiles, to analyze the behavior of the overlap probability distribution of the Sherrington-Kirkpatrick and 3D Edwards-Anderson models of Ising spin glasses. We find that this approach is an effective tool to distinguish between replica symmetry breaking-like and droplet-like behavior of the spin-glass phase. Our results are in agreement with a replica symmetry breaking-like behavior for the 3D Edwards-Anderson model.

  4. Spin dynamics in the anisotropic spin glass Fe2TiO5

    DEFF Research Database (Denmark)

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

    1985-01-01

    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 results...

  5. Instability of spin glass phase in divalent iron phosphate glass under a magnetic field

    Science.gov (United States)

    Nakatsuka, Yuko; Murai, Shunsuke; Fujita, Koji; Tanaka, Katsuhisa

    2017-01-01

    The spin glass behaviour of 50FeO · 50P2O5 (in mol%) glass has been examined under finite magnetic fields. The Sherrington-Kirkpatrick (SK) model, i.e. the mean field theory, is unsuitable for the interpretation of the frequency dependence of the ac magnetic susceptibility observed under an external field of 0.1 T; the critical exponent derived from the SK model is unphysically large. On the other hand, the droplet model explains well the frequency and field dependence of the spin-freezing temperature and the exponent of the thermally activated process is within the range defined by the droplet model. The results indicate that the spin glass phase of the 50FeO · 50P2O5 glass is unstable against magnetic fields.

  6. Manganite/Cuprate Superlattice as Artificial Reentrant Spin Glass

    KAUST Repository

    Ding, Junfeng

    2016-05-04

    Emerging physical phenomena at the unit-cell-controlled interfaces of transition-metal oxides have attracted lots of interest because of the rich physics and application opportunities. This work reports a reentrant spin glass behavior with strong magnetic memory effect discovered in oxide heterostructures composed of ultrathin manganite La0.7Sr0.3MnO3 (LSMO) and cuprate La2CuO4 (LCO) layers. These heterostructures are featured with enhanced ferromagnetism before entering the spin glass state: a Curie temperature of 246 K is observed in the superlattice with six-unit-cell LSMO layers, while the reference LSMO film with the same thickness shows much weaker magnetism. Furthermore, an insulator-metal transition emerges at the Curie temperature, and below the freezing temperature the superlattices can be considered as a glassy ferromagnetic insulator. These experimental results are closely related to the interfacial spin reconstruction revealed by the first-principles calculations, and the dependence of the reentrant spin glass behavior on the LSMO layer thickness is in line with the general phase diagram of a spin system derived from the infinite-range SK model. The results of this work underscore the manganite/cuprate superlattices as a versatile platform of creating artificial materials with tailored interfacial spin coupling and physical properties. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Stability of the Spin Glass Phase under Perturbations

    CERN Document Server

    Contucci, Pierluigi; Giberti, Claudio

    2011-01-01

    We introduce and prove a new stability property of the quenched equilibrium state for the spin glass phase and show that it implies the whole set of Ghirlanda-Guerra identities. The new stability deals with perturbations which reproduces both thermal and disorder fluctuations, thus generalizing the standard stochastic stability of disordered systems.

  8. Temperature dependence of fluctuation time scales in spin glasses

    DEFF Research Database (Denmark)

    Kenning, Gregory G.; Bowen, J.; Sibani, Paolo;

    2010-01-01

    Using a series of fast cooling protocols we have probed aging effects in the spin glass state as a function of temperature. Analyzing the logarithmic decay found at very long time scales within a simple phenomenological barrier model, leads to the extraction of the fluctuation time scale of the s...

  9. Temperature dependence of fluctuation time scales in spin glasses

    DEFF Research Database (Denmark)

    Kenning, Gregory G.; Bowen, J.; Sibani, Paolo

    2010-01-01

    a generalized Arrhenius law. We discuss the hypothesis that, upon cooling to a measuring temperature within the spin glass state, there is a range of dynamically in-equivalent configurations in which the system can be trapped, and check within a numerical barrier model simulation, that this  leads to sub...

  10. Linear and cubic dynamic susceptibilities in quantum spin glass

    CERN Document Server

    Busiello, G; Sushkova, V G

    2001-01-01

    The low temperature behaviour of the dynamic nonlinear (cubic) susceptibility chi sub 3 sup ' (omega, T) in quantum d-dimensional Ising spin glass with short-range interactions between spins is investigated in terms of the quantum droplet model and the quantum-mechanical nonlinear response theory is employed. We have revealed a glassy like behaviour of droplet dynamics. The frequency dependence of chi sub 3 sup ' (omega, T) is very remarkable, the temperature dependence is found at very low temperatures (quantum regime). The nonlinear response depends on the tunneling rate for a droplet which regulates the strength of quantum fluctuations. This response has a strong dependence on the distribution of droplet free energies and on the droplet length scale average. Implications for experiments in quantum spin glasses like disordered dipolar quantum Ising magnet LiHo sub x Y sub 1 sub - sub x F sub 4 and pseudospin are noted.

  11. Orientational glass: Full replica symmetry breaking in generalized spin glass-like models without reflection symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Tareyeva, E.E. [Institute for High Pressure Physics, Russian Academy of Sciences, 142190 Troitsk (Russian Federation); Schelkacheva, T.I., E-mail: tanschelk@gmail.com [Institute for High Pressure Physics, Russian Academy of Sciences, 142190 Troitsk (Russian Federation); Chtchelkatchev, N.M. [Institute for High Pressure Physics, Russian Academy of Sciences, 142190 Troitsk (Russian Federation); L.D. Landau Institute for Theoretical Physics, Russian Academy of Sciences, 117940 Moscow (Russian Federation); Department of Theoretical Physics, Moscow Institute of Physics and Technology, 141700 Moscow (Russian Federation)

    2013-02-15

    We investigate near the point of glass transition the expansion of the free energy corresponding to the generalized Sherrington–Kirkpatrick model with arbitrary diagonal operators U{sup -hat} standing instead of Ising spins. We focus on the case when U{sup -hat} is an operator with broken reflection symmetry. Such a consideration is important for understanding the behavior of spin glass-like phases in a number of real physical systems, mainly in orientational glasses in mixed molecular crystals which present just the case. We build explicitly a full replica symmetry breaking (FRSB) solution of the equations for the orientational glass order parameters when the nonsymmetric part of U{sup -hat} is small. This particular result presents a counterexample in the context of usually adopted conjecture of the absence of FRSB solution in systems with no reflection symmetry.

  12. Orientational glass: Full replica symmetry breaking in generalized spin glass-like models without reflection symmetry

    Science.gov (United States)

    Tareyeva, E. E.; Schelkacheva, T. I.; Chtchelkatchev, N. M.

    2013-02-01

    We investigate near the point of glass transition the expansion of the free energy corresponding to the generalized Sherrington-Kirkpatrick model with arbitrary diagonal operators Uˆ standing instead of Ising spins. We focus on the case when Uˆ is an operator with broken reflection symmetry. Such a consideration is important for understanding the behavior of spin glass-like phases in a number of real physical systems, mainly in orientational glasses in mixed molecular crystals which present just the case. We build explicitly a full replica symmetry breaking (FRSB) solution of the equations for the orientational glass order parameters when the nonsymmetric part of Uˆ is small. This particular result presents a counterexample in the context of usually adopted conjecture of the absence of FRSB solution in systems with no reflection symmetry.

  13. Avalanches and hysteresis in frustrated superconductors and XY spin glasses.

    Science.gov (United States)

    Sharma, Auditya; Andreanov, Alexei; Müller, Markus

    2014-10-01

    We study avalanches along the hysteresis loop of long-range interacting spin glasses with continuous XY symmetry, which serves as a toy model of granular superconductors with long-range and frustrated Josephson couplings. We identify sudden jumps in the T=0 configurations of the XY phases as an external field is increased. They are initiated by the softest mode of the inverse susceptibility matrix becoming unstable, which induces an avalanche of phase updates (or spin alignments). We analyze the statistics of these events and study the correlation between the nonlinear avalanches and the soft mode that initiates them. We find that the avalanches follow the directions of a small fraction of the softest modes of the inverse susceptibility matrix, similarly as was found in avalanches in jammed systems. In contrast to the similar Ising spin glass (Sherrington-Kirkpatrick) studied previously, we find that avalanches are not distributed with a scale-free power law but rather have a typical size which scales with the system size. We also observe that the Hessians of the spin-glass minima are not part of standard random matrix ensembles as the lowest eigenvector has a fractal support.

  14. Short-range spin glasses and Random Overlap Structures

    CERN Document Server

    Arguin, Louis-Pierre

    2010-01-01

    Properties of Random Overlap Structures (ROSt)'s constructed from the Edwards-Anderson (EA) Spin Glass model on $\\Z^d$ with periodic boundary conditions are studied. ROSt's are $\\N\\times\\N$ random matrices whose entries are the overlaps of spin configurations sampled from the Gibbs measure. Since the ROSt construction is the same for mean-field models (like the Sherrington-Kirkpatrick model) as for short-range ones (like the EA model), the setup is a good common ground to study the effect of dimensionality on the properties of the Gibbs measure. In this spirit, it is shown, using translation invariance, that the ROSt of the EA model possesses a local stability that is stronger than stochastic stability, a property known to hold at almost all temperatures in many spin glass models with Gaussian couplings. This fact is used to prove stochastic stability for the EA spin glass at all temperatures and for a wide range of coupling distributions. On the way, a theorem of Newman and Stein about the pure state decompo...

  15. Replica symmetry breaking transition of the weakly anisotropic Heisenberg spin glass in magnetic fields.

    Science.gov (United States)

    Imagawa, Daisuke; Kawamura, Hikaru

    2004-02-20

    The spin and the chirality orderings of the three-dimensional Heisenberg spin glass with the weak random anisotropy are studied under applied magnetic fields by equilibrium Monte Carlo simulations. A replica symmetry breaking transition occurs in the chiral sector accompanied by the simultaneous spin-glass order. The ordering behavior differs significantly from that of the Ising spin glass, despite the similarity in the global symmetry. Our observation is consistent with the spin-chirality decoupling-recoupling scenario of a spin-glass transition.

  16. Pair correlation function for spin glasses

    Science.gov (United States)

    Fernández, Julio F.; Alonso, Juan J.

    2012-10-01

    We extract a pair correlation function (PCF) from probability distributions of the spin-overlap parameter q. The distributions come from Monte Carlo simulations. A measure, w, of the thermal fluctuations of magnetic patterns follows from the PCFs. We also obtain rms deviations (over different system samples) δp away from average probabilities for q. For the linear system sizes L that we have studied, w and δp are independent of L in the Edwards-Anderson model but scale as 1/L and L, respectively, in the Sherrington-Kirkpatrick model.

  17. Spin-glass behavior in zero magnetic field using tunnel resistance

    Energy Technology Data Exchange (ETDEWEB)

    Takeuchi, Y. [Department of Applied Physics and Physico-Infomatics, Faculty of Science and Technology, Keio University, Yokohama 223-8522 (Japan)]. E-mail: takeuchi@az.appi.keio.ac.jp; Komatsu, K. [Department of Applied Physics and Physico-Infomatics, Faculty of Science and Technology, Keio University, Yokohama 223-8522 (Japan); Maki, H. [Department of Applied Physics and Physico-Infomatics, Faculty of Science and Technology, Keio University, Yokohama 223-8522 (Japan); Taniyama, T. [Materials and Structures Laboratory, Tokyo Institute of Technology, 4529 Nagatsuta, Midori, Yokohama 226-8503 (Japan); Sato, T. [Department of Applied Physics and Physico-Infomatics, Faculty of Science and Technology, Keio University, Yokohama 223-8522 (Japan)

    2007-03-15

    The measurement of spin glass in zero magnetic field is essential to investigate the intrinsic nature of spin glass. We pay attention to tunnel resistance between spin-glass layers. The temperature dependence of tunnel resistance between spin-glass layers with the structure of AgMn/Al{sub 2}O{sub 3}/AgMn was measured, and was compared with that of Al/Al{sub 2}O{sub 3}/AgMn. For the junction of AgMn/Al{sub 2}O{sub 3}/AgMn, tunnel resistance shows a peak around the spin-glass transition temperature, but no peak was observed for the junction of Al/Al{sub 2}O{sub 3}/AgMn. The results indicate that the magnetic correlation between spin-glass layers is reflected to tunnel resistance. The singularity of the tunnel resistance between spin-glass layers is discussed by the droplet theory.

  18. Spin-glass transition in Heisenberg spin system with ± J random bonds

    Science.gov (United States)

    Ghazali, A.; Lallemand, P.; Diep, H. T.

    1986-02-01

    We investigate by Monte Carlo simulations the simple cubic lattice with Heisenberg spins interacting via short range ± J random bonds for different antiferromagnetic bond concentrations x. We find that for x<0.25, a transition of the para-ferromagnetic type occurs. For 0.25⪅ x⩽0.5, the existence of a remanant magnetization and of a rounded peak of the specific heat together with other data support a paramagnetic-spin-glass transition at finite temperature.

  19. Chaotic nature of the spin-glass phase

    Science.gov (United States)

    Bray, A. J.; Moore, M. A.

    1987-01-01

    The microscopic structure of the ordered phase of spin glasses is investigated theoretically in the framework of the T = 0 fixed-point model (McMillan, 1984; Fisher and Huse, 1986; and Bray and Moore, 1986). The sensitivity of the ground state to changes in the interaction strengths at T = 0 is explored, and it is found that for sufficiently large length scales the ground state is unstable against arbitrarily weak perturbations to the bonds. Explicit results are derived for d = 1, and the implications for d = 2 and d = 3 are considered in detail. It is concluded that there is no hidden order pattern for spin glasses at all T less than T(C), the ordered-phase spin correlations being chaotic functions of spin separation at fixed temperature or of temperature (for a given pair of spins) at scale lengths L greater than (T delta T) exp -1/zeta, where zeta = d(s)/2 - y, d(s) is the interfacial fractal dimension, and -y is the thermal eigenvalue at T = 0.

  20. Interface free energies in p-spin glass models.

    Science.gov (United States)

    Moore, M A

    2006-04-07

    The replica method is used to calculate the interface free energy associated with the change from periodic to antiperiodic boundary conditions in finite-dimensional p-spin glass models in the phase which at mean-field level has one-step replica symmetry breaking (1RSB). In any finite dimension the interface free energy is exponentially small for a large system. This result implies that, in finite dimensions, the 1RSB state does not exist, as it is destroyed by thermal excitation of arbitrarily large droplets. The implications of this for the theory of structural glasses are discussed.

  1. Diagonal stripes in the spin glass phase of cuprates

    Energy Technology Data Exchange (ETDEWEB)

    Seibold, G., E-mail: goetz@physik.tu-cottbus.d [Institut fuer Physik, BTU Cottbus, Post Box 101344, 03013 Cottbus (Germany); Lorenzana, J. [SMC-INFM-CNR and Dipartimento di Fisica, Universita di Roma ' La Sapienza' , P.le Aldo Moro 5, I-00185 Roma (Italy)

    2010-12-15

    Based on the unrestricted Gutzwiller approximation we study the possibility that the diagonal incommensurate spin scattering in the spin glass phase of lanthanum cuprates originates from stripe formation. Similar to the metallic phase two types of diagonal stripe structures appear to be stable: (a) site-centered textures which have one hole per site along the stripe and (b) ferromagnetic stair-case structures which are the diagonal equivalent to bond-centered stripes in the metallic phase and which on average have a filling of 3/4 holes per stripe site. We give a detailed analysis of the stability of both diagonal textures with regard to the vertical ones.

  2. Partition function zeros of an Ising spin glass

    CERN Document Server

    Damgaard, P H

    1995-01-01

    We study the pattern of zeros emerging from exact partition function evaluations of Ising spin glasses on conventional finite lattices of varying sizes. A large number of random bond configurations are probed in the framework of quenched averages. This study is motivated by the relationship between hierarchical lattice models whose partition function zeros fall on Julia sets and chaotic renormalization flows in such models with frustration, and by the possible connection of the latter with spin glass behaviour. In any finite volume, the simultaneous distribution of the zeros of all partition functions can be viewed as part of the more general problem of finding the location of all the zeros of a certain class of random polynomials with positive integer coefficients. Some aspects of this problem have been studied in various branches of mathematics, and we show how polynomial mappings which are used in graph theory to classify graphs, may help in characterizing the distribution of zeros. We finally discuss the ...

  3. Parallel tempering and 3D spin glass models

    Science.gov (United States)

    Papakonstantinou, T.; Malakis, A.

    2014-03-01

    We review parallel tempering schemes and examine their main ingredients for accuracy and efficiency. We discuss two selection methods of temperatures and some alternatives for the exchange of replicas, including all-pair exchange methods. We measure specific heat errors and round-trip efficiency using the two-dimensional (2D) Ising model, and also test the efficiency for the ground state production in 3D spin glass models. We find that the optimization of the GS problem is highly influenced by the choice of the temperature range of the PT process. Finally, we present numerical evidence concerning the universality aspects of an anisotropic case of the 3D spin-glass model.

  4. Random Overlap Structures: Properties and Applications to Spin Glasses

    CERN Document Server

    Arguin, Louis-Pierre

    2010-01-01

    Random Overlap Structures (ROSt's) are random elements on the space of probability measures on the unit ball of a Hilbert space, where two measures are identified if they differ by an isometry. In spin glasses, they arise as natural limits of Gibbs measures under the appropriate algebra of functions. We prove that the so called `cavity mapping' on the space of ROSt's is continuous, leading to a proof of the stochastic stability conjecture for the limiting Gibbs measures of a large class of spin glass models. Similar arguments yield the proofs of a number of other properties of ROSt's that may be useful in future attempts at proving the ultrametricity conjecture. Lastly, assuming that the ultrametricity conjecture holds, the setup yields a constructive proof of the Parisi formula for the free energy of the Sherrington-Kirkpatrick model by making rigorous a heuristic of Aizenman, Sims and Starr.

  5. Is there an Almeida Thouless line in spin glasses?

    Science.gov (United States)

    Young, A. P.

    2008-03-01

    One of the most striking predictions of the mean field of spin glasses is a line of transitions in the magnetic field temperature plane, called the Almeida-Thouless (AT) line, which separates a high temperature, paramagnetic phase, with finite relaxation times, from a low temperature spin glass phase with infinite relaxation times. It is therefore represents an ergodic to non-ergodic transition with no change in symmetry. Whether or not an AT line occurs in real spin glasses has been controversial. Experiments have looked to see if there is a divergent relaxation time at finite field, and Ref. [1], for example, has argued their data indicates no AT line. However, other experimental papers have come to the opposite conclusion. Theoretically, it seems best to investigate a divergent static quantity, the ``replicon'' susceptibility (which is not accessible experimentally), and the corresponding correlation length. A finite size scaling analysis of the three-dimensional Ising spin glass in a field [2] found no AT line. It is, however, possible that an AT line could occur in higher dimensions, even if it does not occur in d=3. To investigate this question we used an analogous model, a one-dimensional system with long-range interactions which fall off with a power law, in which varying the power is analogous to varying the dimension in the short-range case. We do find an AT line [3] in models corresponding to short-range systems in dimension greater than 6.[1] J. Mattsson, T. Jonsson, P. Nordblad, H. A. Katori, and A. Ito, Phys. Rev. Lett. 74, 4305 (1995).[2] A.P. Young and Helmut G. Katzgraber, Phys. Rev. Lett. 93, 207203 (2004).[3] Helmut G. Katzgraber and A.P. Young, Phys. Rev. E 72, 184416 (2005).

  6. Fluctuation dissipation relation in an ageing spin glass

    Energy Technology Data Exchange (ETDEWEB)

    Herisson, D. E-mail: didier.herisson@angstrom.uu.se; Ocio, M

    2004-05-01

    The time autocorrelation of magnetic fluctuations C(t',t) has been measured in a spin glass, and compared with the magnetic response {chi}(t',t). Clearly, we observe a non-linear fluctuation dissipation relation between C and {chi}. A scaling procedure allows us to extrapolate to the limit of long waiting times t', where the {chi}(C) relationship should become independent of t'.

  7. Reentrance and ultrametricity in three-dimensional Ising spin glasses

    Science.gov (United States)

    Katzgraber, Helmut G.; Thomas, Creighton K.; Hartmann, Alexander K.

    2012-02-01

    We study the three-dimensional Edwards-Anderson Ising spin glass with bimodal disorder with a fraction of 22.8% antiferromagnetic bonds. Parallel tempering Monte Carlo simulations down to very low temperatures show that for this fraction of antiferromagnetic bonds the phase diagram of the system is reentrant, in agreement with previous results. Furthemore, using a clustering analysis, we analyze the ultrametric properties of phase space for this model.

  8. Fluctuation Bounds For Interface Free Energies in Spin Glasses

    Science.gov (United States)

    Arguin, L.-P.; Newman, C. M.; Stein, D. L.; Wehr, J.

    2014-07-01

    We consider the free energy difference restricted to a finite volume for certain pairs of incongruent thermodynamic states (if they exist) in the Edwards-Anderson Ising spin glass at nonzero temperature. We prove that the variance of this quantity with respect to the couplings grows proportionally to the volume in any dimension greater than or equal to two. As an illustration of potential applications, we use this result to restrict the possible structure of Gibbs states in two dimensions.

  9. Replica symmetry breaking in cold atoms and spin glasses

    Science.gov (United States)

    Rotondo, P.; Tesio, E.; Caracciolo, S.

    2015-01-01

    We consider a system composed by N atoms trapped within a multimode cavity, whose theoretical description is captured by a disordered multimode Dicke model. We show that in the resonant, zero-field limit the system exactly realizes the Sherrington-Kirkpatrick model. Upon a redefinition of the temperature, the same dynamics is realized in the dispersive, strong-field limit. This regime also gives access to spin-glass observables which can be used to detect replica symmetry breaking.

  10. The glass crossover from mean-field Spin-Glasses to supercooled liquids

    Science.gov (United States)

    Rizzo, Tommaso

    2016-03-01

    Stochastic-Beta-Relaxation provides a characterisation of the glass crossover in discontinuous Spin-Glasses and supercoooled liquid. Notably it can be derived through a rigorous computation from a dynamical Landau theory. In this paper, I will discuss the precise meaning of this connection in a language that does not require familiarity with statistical field theory. I will discuss finite-size corrections in mean-field Spin-Glass models and loop corrections in finite-dimensional models that are both described by the dynamical Landau theory considered. Then I will argue that the same Landau theory can be associated to supercooled liquid described by Mode-Coupling Theory invoking a physical principle of time-scale invariance.

  11. Spin Glass Models of Syntax and Language Evolution

    CERN Document Server

    Siva, Karthik; Marcolli, Matilde

    2015-01-01

    Using the SSWL database of syntactic parameters of world languages, and the MIT Media Lab data on language interactions, we construct a spin glass model of language evolution. We treat binary syntactic parameters as spin states, with languages as vertices of a graph, and assigned interaction energies along the edges. We study a rough model of syntax evolution, under the assumption that a strong interaction energy tends to cause parameters to align, as in the case of ferromagnetic materials. We also study how the spin glass model needs to be modified to account for entailment relations between syntactic parameters. This modification leads naturally to a generalization of Potts models with external magnetic field, which consists of a coupling at the vertices of an Ising model and a Potts model with q=3, that have the same edge interactions. We describe the results of simulations of the dynamics of these models, in different temperature and energy regimes. We discuss the linguistic interpretation of the paramete...

  12. Ordering of the three-dimensional Heisenberg spin glass in magnetic fields.

    Science.gov (United States)

    Kawamura, H; Imagawa, D

    2001-11-12

    Spin and chirality orderings of the three-dimensional Heisenberg spin glass are studied under magnetic fields in light of the recently developed spin-chirality decoupling-recoupling scenario. It is found by Monte Carlo simulations that the chiral-glass transition and the chiral-glass ordered state, which are essentially of the same character as their zero-field counterparts, occur under magnetic fields. The implication to the experimental phase diagram is discussed.

  13. Coexistence of exponentially many chaotic spin-glass attractors.

    Science.gov (United States)

    Peleg, Y; Zigzag, M; Kinzel, W; Kanter, I

    2011-12-01

    A chaotic network of size N with delayed interactions which resembles a pseudoinverse associative memory neural network is investigated. For a load α = P/N chaotic network functions as an associative memory of 2P attractors with macroscopic basin of attractions which decrease with α. At finite α, a chaotic spin-glass phase exists, where the number of distinct chaotic attractors scales exponentially with N. Each attractor is characterized by a coexistence of chaotic behavior and freezing of each one of the N chaotic units or freezing with respect to the P patterns. Results are supported by large scale simulations of networks composed of Bernoulli map units and Mackey-Glass time delay differential equations.

  14. Optimized GPU simulation of continuous-spin glass models

    CERN Document Server

    Yavors'kii, Taras

    2012-01-01

    We develop a highly optimized code for simulating the Edwards-Anderson Heisenberg model on graphics processing units (GPUs). Using a number of computational tricks such as tiling, data compression and appropriate memory layouts, the simulation code combining over-relaxation, heat bath and parallel tempering moves achieves a peak performance of 0.29 ns per spin update on realistic system sizes, corresponding to a more than 150 fold speed-up over a serial CPU reference implementation. The optimized implementation is used to study the spin-glass transition in a random external magnetic field to probe the existence of a de Almeida-Thouless line in the model, for which we give benchmark results.

  15. Optimized GPU simulation of continuous-spin glass models

    Science.gov (United States)

    Yavors'kii, T.; Weigel, M.

    2012-08-01

    We develop a highly optimized code for simulating the Edwards-Anderson Heisenberg model on graphics processing units (GPUs). Using a number of computational tricks such as tiling, data compression and appropriate memory layouts, the simulation code combining over-relaxation, heat bath and parallel tempering moves achieves a peak performance of 0.29 ns per spin update on realistic system sizes, corresponding to a more than 150 fold speed-up over a serial CPU reference implementation. The optimized implementation is used to study the spin-glass transition in a random external magnetic field to probe the existence of a de Almeida-Thouless line in the model, for which we give benchmark results.

  16. Defect energy of infinite-component vector spin glasses.

    Science.gov (United States)

    Lee, L W; Young, A P

    2005-09-01

    We compute numerically the zero-temperature defect energy DeltaE of the vector spin glass in the limit of an infinite number of spin components m , for a range of dimensions 2< or d < or =5 . Fitting to DeltaE approximately L(theta) , where L is the system size, we obtain: theta similar to-1.54 (d=2) , theta similar to-1.04 (d=3) , theta similar to -0.67 (d=4) , and theta similar to -0.37 (d=5) . These results show that the lower critical dimension dl (the dimension where theta changes sign) is significantly higher for m=infinity than for finite m (where 2< dl <3 ).

  17. Overfrustrated and underfrustrated spin glasses in d =3 and 2: Evolution of phase diagrams and chaos including spin-glass order in d =2

    Science.gov (United States)

    Ilker, Efe; Berker, A. Nihat

    2014-04-01

    In spin-glass systems, frustration can be adjusted continuously and considerably, without changing the antiferromagnetic bond probability p, by using locally correlated quenched randomness, as we demonstrate here on hypercubic lattices and hierarchical lattices. Such overfrustrated and underfrustrated Ising systems on hierarchical lattices in d =3 and 2 are studied. With the removal of just 51% of frustration, a spin-glass phase occurs in d =2. With the addition of just 33% frustration, the spin-glass phase disappears in d =3. Sequences of 18 different phase diagrams for different levels of frustration are calculated in both dimensions. In general, frustration lowers the spin-glass ordering temperature. At low temperatures, increased frustration favors the spin-glass phase (before it disappears) over the ferromagnetic phase and symmetrically the antiferromagnetic phase. When any amount, including infinitesimal, frustration is introduced, the chaotic rescaling of local interactions occurs in the spin-glass phase. Chaos increases with increasing frustration, as can be seen from the increased positive value of the calculated Lyapunov exponent λ, starting from λ =0 when frustration is absent. The calculated runaway exponent yR of the renormalization-group flows decreases with increasing frustration to yR=0 when the spin-glass phase disappears. From our calculations of entropy and specific-heat curves in d =3, it is shown that frustration lowers in temperature the onset of both long- and short-range order in spin-glass phases, but is more effective on the former. From calculations of the entropy as a function of antiferromagnetic bond concentration p, it is shown that the ground-state and low-temperature entropy already mostly sets in within the ferromagnetic and antiferromagnetic phases, before the spin-glass phase is reached.

  18. Overfrustrated and underfrustrated spin glasses in d=3 and 2: evolution of phase diagrams and chaos including spin-glass order in d=2.

    Science.gov (United States)

    Ilker, Efe; Berker, A Nihat

    2014-04-01

    In spin-glass systems, frustration can be adjusted continuously and considerably, without changing the antiferromagnetic bond probability p, by using locally correlated quenched randomness, as we demonstrate here on hypercubic lattices and hierarchical lattices. Such overfrustrated and underfrustrated Ising systems on hierarchical lattices in d=3 and 2 are studied. With the removal of just 51% of frustration, a spin-glass phase occurs in d=2. With the addition of just 33% frustration, the spin-glass phase disappears in d=3. Sequences of 18 different phase diagrams for different levels of frustration are calculated in both dimensions. In general, frustration lowers the spin-glass ordering temperature. At low temperatures, increased frustration favors the spin-glass phase (before it disappears) over the ferromagnetic phase and symmetrically the antiferromagnetic phase. When any amount, including infinitesimal, frustration is introduced, the chaotic rescaling of local interactions occurs in the spin-glass phase. Chaos increases with increasing frustration, as can be seen from the increased positive value of the calculated Lyapunov exponent λ, starting from λ=0 when frustration is absent. The calculated runaway exponent yR of the renormalization-group flows decreases with increasing frustration to yR=0 when the spin-glass phase disappears. From our calculations of entropy and specific-heat curves in d=3, it is shown that frustration lowers in temperature the onset of both long- and short-range order in spin-glass phases, but is more effective on the former. From calculations of the entropy as a function of antiferromagnetic bond concentration p, it is shown that the ground-state and low-temperature entropy already mostly sets in within the ferromagnetic and antiferromagnetic phases, before the spin-glass phase is reached.

  19. Dynamical TAP equations for non-equilibrium Ising spin glasses

    DEFF Research Database (Denmark)

    Roudi, Yasser; Hertz, John

    2011-01-01

    equations take the form of self consistent equations for magnetizations at time t+1, given the magnetizations at time t. In the asynchronously updated model, the TAP equations determine the time derivatives of the magnetizations at each time, again via self consistent equations, given the current values......We derive and study dynamical TAP equations for Ising spin glasses obeying both synchronous and asynchronous dynamics using a generating functional approach. The system can have an asymmetric coupling matrix, and the external fields can be time-dependent. In the synchronously updated model, the TAP...

  20. Interface free energies in p-spin glass models

    OpenAIRE

    2006-01-01

    The replica method has been used to calculate the interface free energy associated with the change from periodic to anti-periodic boundary conditions in finite-dimensional p-spin glass models in the phase which at mean-field level has one-step replica symmetry breaking (1RSB). In any finite dimension the interface free energy is exponentially small for a large system. This result implies that in finite dimensions, the 1RSB state does not exist, as it is destroyed by thermal excitation of arbi...

  1. Population Annealing: Theory and Application in Spin Glasses

    Science.gov (United States)

    Machta, Jonathan; Wang, Wenlong; Katzgraber, Helmut G.

    Population annealing is an efficient sequential Monte Carlo algorithm for simulating equilibrium states of systems with rough free energy landscapes. The theory of population annealing is presented, and systematic and statistical errors are discussed. The behavior of the algorithm is studied in the context of large-scale simulations of the three-dimensional Ising spin glass and the performance of the algorithm is compared to parallel tempering. It is found that the two algorithms are similar in efficiency though with different strengths and weaknesses. Supported by NSF DMR-1151387, DMR-1208046 and DMR-1507506.

  2. Polymers on disordered trees, spin glasses, and traveling waves

    Energy Technology Data Exchange (ETDEWEB)

    Derrida, B.; Spohn, H.

    1988-06-01

    We show that the problem of a directed polymer on a tree with disorder can be reduced to the study of nonlinear equations of reaction-diffusion type. These equations admit traveling wave solutions that move at all possible speeds above a certain minimal speed. The speed of the wavefront is the free energy of the polymer problem and the minimal speed corresponds to a phase transition to a glassy phase similar to the spin-glass phase. Several properties of the polymer problem can be extracted from the correspondence with the traveling wave: probability distribution of the free energy, overlaps, etc.

  3. Strange attractor in the Potts spin glass on hierarchical lattices

    Energy Technology Data Exchange (ETDEWEB)

    Lima, Washington de [Universidade Federal de Pernambuco, Centro Acadêmico do Agreste, Pernambuco (Brazil); Camelo-Neto, G. [Universidade Federal de Alagoas, Núcleo de Ciências Exatas, Laboratório de Física Teórica e Computacional, CEP 57309-005 Arapiraca, Alagoas (Brazil); Coutinho, S., E-mail: sergio@ufpe.br [Universidade Federal de Pernambuco, Departamento de Física, Laboratório de Física Teórica e Computacional, Cidade Universitária, CEP 50670-901 Recife, Pernambuco (Brazil)

    2013-11-29

    The spin-glass q-state Potts model on d-dimensional diamond hierarchical lattices is investigated by an exact real space renormalization group scheme. Above a critical dimension d{sub l}(q) for q>2, the coupling constants probability distribution flows to a low-temperature strange attractor or to the high-temperature paramagnetic fixed point, according to the temperature is below or above the critical temperature T{sub c}(q,d). The strange attractor was investigated considering four initial different distributions for q=3 and d=5 presenting strong robustness in shape and temperature interval suggesting a condensed phase with algebraic decay.

  4. Inference from matrix products: a heuristic spin glass algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Hastings, Matthew B [Los Alamos National Laboratory

    2008-01-01

    We present an algorithm for finding ground states of two-dimensional spin-glass systems based on ideas from matrix product states in quantum information theory. The algorithm works directly at zero temperature and defines an approximation to the energy whose accuracy depends on a parameter k. We test the algorithm against exact methods on random field and random bond Ising models, and we find that accurate results require a k which scales roughly polynomially with the system size. The algorithm also performs well when tested on small systems with arbitrary interactions, where no fast, exact algorithms exist. The time required is significantly less than Monte Carlo schemes.

  5. Exchange bias effect in spin glass CoCr{sub 2}O{sub 4} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Changming; Tian, Zhaoming; Wang, Liguang; Yuan, Songliu, E-mail: yuansl@hust.edu.cn

    2015-11-01

    CoCr{sub 2}O{sub 4} nanoparticles are about 5.4 nm in diameter synthesized by a hydrothermal technique. Magnetization measurements reveal that the nanoparticles exhibit a spin glass behavior below glass transition temperature. Signature of memory effect is clear in reheating curve where the step-like shape increasing with the increase of temperature is recovered after cooling process. Magnetic relaxation is performed to prove memory effect. Ageing effect is also detected in CoCr{sub 2}O{sub 4} nanoparticles to verify the spin glass behavior. As temperature decreases to 5 K, which is far below the glass transition temperature, exchange bias effect can be observed clearly accompanied with a shift in field-cooled hysteresis loop. As particle size decreases to 5.4 nm, spin glass behavior appears due to the increased spin disorder effect. The spin glass phase providing a pinning force from some frozen spins to the rotatable spins gives the key to explain the exchange bias effects. - Highlights: • Existence of spin glass phase is verified in CoCr{sub 2}O{sub 4} nanoparticles. • Exchange bias effect with a shift in field-cooled loop is observed at 5 K. • It is proved that exchange bias effect is originated from the spin glass phase.

  6. Spin Glass Field Theory with Replica Fourier Transforms

    Science.gov (United States)

    Pimentel, Iveta R.; De Dominicis, Cirano

    We develop a field theory for spin glasses using Replica Fourier Transforms (RFT). We present the formalism for the case of replica symmetry and the case of replica symmetry breaking on an ultrametric tree, with the number of replicas n and the number of replica symmetry breaking steps R generic integers. We show how the RFT applied to the two-replica fields allows to construct a new basis which block-diagonalizes the four-replica mass-matrix, into the replicon, anomalous and longitudinal modes. The eigenvalues are given in terms of the mass RFT and the propagators in the RFT space are obtained by inversion of the block-diagonal matrix. The formalism allows to express any i-replica vertex in the new RFT basis and hence enables to perform a standard perturbation expansion. We apply the formalism to calculate the contribution of the Gaussian fluctuations around the Parisi's solution for the free-energy of an Ising spin glass.

  7. Disorder chaos and multiple valleys in spin glasses

    CERN Document Server

    Chatterjee, Sourav

    2009-01-01

    We prove that the Sherrington-Kirkpatrick model of spin glasses is chaotic under small perturbations of the couplings at any temperature in the absence of an external field. The result is proved for two kinds of perturbations: (a) distorting the couplings via Ornstein-Uhlenbeck flows, and (b) replacing a small fraction of the couplings by independent copies. We further prove that the S-K model exhibits multiple valleys in its energy landscape, i.e. there are many states with near-minimal energy that are mutually nearly orthogonal. We show that the variance of the free energy of the S-K model is unusually small at any temperature. (By `unusually small' we mean that it is much smaller than the number of sites; in other words, it beats the classical Gaussian concentration inequality, a phenomenon that we call `superconcentration'.) We prove that the bond overlap in the Edwards-Anderson model of spin glasses is not chaotic under perturbations of the couplings, even large perturbations. Lastly, we obtain sharp low...

  8. Spin Glass a Bridge Between Quantum Computation and Statistical Mechanics

    Science.gov (United States)

    Ohzeki, Masayuki

    2013-09-01

    In this chapter, we show two fascinating topics lying between quantum information processing and statistical mechanics. First, we introduce an elaborated technique, the surface code, to prepare the particular quantum state with robustness against decoherence. Interestingly, the theoretical limitation of the surface code, accuracy threshold, to restore the quantum state has a close connection with the problem on the phase transition in a special model known as spin glasses, which is one of the most active researches in statistical mechanics. The phase transition in spin glasses is an intractable problem, since we must strive many-body system with complicated interactions with change of their signs depending on the distance between spins. Fortunately, recent progress in spin-glass theory enables us to predict the precise location of the critical point, at which the phase transition occurs. It means that statistical mechanics is available for revealing one of the most interesting parts in quantum information processing. We show how to import the special tool in statistical mechanics into the problem on the accuracy threshold in quantum computation. Second, we show another interesting technique to employ quantum nature, quantum annealing. The purpose of quantum annealing is to search for the most favored solution of a multivariable function, namely optimization problem. The most typical instance is the traveling salesman problem to find the minimum tour while visiting all the cities. In quantum annealing, we introduce quantum fluctuation to drive a particular system with the artificial Hamiltonian, in which the ground state represents the optimal solution of the specific problem we desire to solve. Induction of the quantum fluctuation gives rise to the quantum tunneling effect, which allows nontrivial hopping from state to state. We then sketch a strategy to control the quantum fluctuation efficiently reaching the ground state. Such a generic framework is called

  9. From Spin Glass to Spin Liquid Ground States in Pyrochlore Molybdates

    Science.gov (United States)

    Clark, Lucy

    Magnetic pyrochlores continue to generate intense interest due to the wealth of interesting behaviours that they can display as a result of their highly frustrated nature. Here we will present our study of the molybdate pyrochlore Lu2Mo2O7, which contains non-magnetic Lu3+ and an antiferromagnetic network of corner-sharing tetrahedra of Mo4+ 4d2 S = 1 ions. Magnetic susceptibility data show that Lu2Mo2O7 enters an unconventional spin glass state at Tf ~ 16 K that displays a quadratic dependence of the low temperature magnetic heat capacity, akin to that observed for its well-studied sister compound Y2Mo2O7. This spin glass transition is also clearly marked in our inelastic (CNCS, SNS) and diffuse elastic magnetic (D7, ILL) neutron scattering data. Furthermore, we will show that it is possible to topochemically substitute the oxide, O2-, ions within Lu2Mo2O7 for nitride, N3-, to produce an oxynitride molybdate pyrochlore of composition Lu2Mo2O5N2. Magnetic susceptibility measurements confirm that strong antiferromagnetic correlations persist within the oxynitride, which contains Mo5+ 4d1 S =1/2 ions and is thus a prime candidate to host exotic quantum spin liquid behavior. We will discuss how the enhanced quantum spin fluctuations in Lu2Mo2O5N2 appear to suppress the spin freezing transition observed in its parent oxide and instead support the formation of a gapless spin liquid phase that displays a linear dependence of the low temperature magnetic heat capacity.

  10. Spin-chirality decoupling in the one-dimensional Heisenberg spin glass with long-range power-law interactions.

    Science.gov (United States)

    Viet, Dao Xuan; Kawamura, Hikaru

    2010-08-27

    We study the issue of the spin-chirality decoupling or coupling in the ordering of the Heisenberg spin glass by performing large-scale Monte Carlo simulations on a one-dimensional Heisenberg spin-glass model with a long-range power-law interaction up to large system sizes. We find that the spin-chirality decoupling occurs for an intermediate range of the power-law exponent. Implications to the corresponding d-dimensional short-range model are discussed.

  11. Irreversible transitions in the exchange-striction model of spin-glass state

    Science.gov (United States)

    Valkov, V. I.; Golovchan, A. V.

    2014-08-01

    Based on the assumption of a negative volume dependence of random exchange integrals, it is possible to switch to a compressible Sherrington-Kirkpatrick spin-glass model. Within the proposed model, temperature-pressure phase diagrams were calculated and pressure- and magnetic-field-induced first-order phase transitions from the initial paramagnetic and spin-glass states to the ferromagnetic state were predicted. It was shown that the application of pressure in the spin-glass state not only increases and shifts magnetic susceptibility, but also reduces the critical magnetic fields of irreversible induced phase transitions from the spin-glass to the ferromagnetic state. The obtained results are used to describe the spin-glass state in (Sm1-xGdx)0.55Sr0.45MnO3.

  12. Reentrant spin glass ordering in an Fe-based bulk metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Qiang; Shen, Jun, E-mail: junshen@tongji.edu.cn [School of Materials Science and Engineering, Tongji University, Shanghai 201804 (China)

    2015-02-07

    We report the results of the complex susceptibility, temperature, and field dependence of DC magnetization and the nonequilibrium dynamics of a bulk metallic glass Fe{sub 40}Co{sub 8}Cr{sub 15}Mo{sub 14}C{sub 15}B{sub 6}Er{sub 2}. Solid indication of the coexistence of reentrant spin glass (SG) and ferromagnetic orderings is determined from both DC magnetization and AC susceptibility under different DC fields. Dynamics scaling of AC susceptibility indicates critical slowing down to a reentrant SG state with a static transition temperature T{sub s} = ∼17.8 K and a dynamic exponent zv = ∼7.3. The SG nature is further corroborated from chaos and memory effects, magnetic hysteresis, and aging behavior. We discuss the results in terms of the competition among random magnetic anisotropy and exchange interactions and compare them with simulation predictions.

  13. The perturbative structure of spin glass field theory

    Science.gov (United States)

    Temesvári, T.

    2014-03-01

    Cubic replicated field theory is used to study the glassy phase of the short-range Ising spin glass just below the transition temperature, and for systems above, at, and slightly below the upper critical dimension six. The order parameter function is computed up to two-loop order. There are two, well-separated bands in the mass spectrum, just as in mean field theory. The small mass band acts as an infrared cutoff, whereas contributions from the large mass region can be computed perturbatively (d>6), or interpreted by the ɛ-expansion around the critical fixed point (d=6-ɛ). The one-loop calculation of the (momentum-dependent) longitudinal mass, and the whole replicon sector is also presented. The innocuous behavior of the replicon masses while crossing the upper critical dimension shows that the ultrametric replica symmetry broken phase remains stable below six dimensions.

  14. The perturbative structure of spin glass field theory

    Energy Technology Data Exchange (ETDEWEB)

    Temesvári, T., E-mail: temtam@helios.elte.hu

    2014-03-15

    Cubic replicated field theory is used to study the glassy phase of the short-range Ising spin glass just below the transition temperature, and for systems above, at, and slightly below the upper critical dimension six. The order parameter function is computed up to two-loop order. There are two, well-separated bands in the mass spectrum, just as in mean field theory. The small mass band acts as an infrared cutoff, whereas contributions from the large mass region can be computed perturbatively (d>6), or interpreted by the ϵ-expansion around the critical fixed point (d=6−ϵ). The one-loop calculation of the (momentum-dependent) longitudinal mass, and the whole replicon sector is also presented. The innocuous behavior of the replicon masses while crossing the upper critical dimension shows that the ultrametric replica symmetry broken phase remains stable below six dimensions.

  15. Thin layer laser bonding using spin-on-glass materials

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Joohan [Department of Mechanical Engineering, Seoul National University of Technology, Seoul, Zip: 139-743 (Korea, Republic of)], E-mail: joohankim@snut.ac.kr; Kim, Hyangtae [Department of Mechanical Engineering, Seoul National University of Technology, Seoul, Zip: 139-743 (Korea, Republic of); Lee, Jae-Hoon [Korea Institute of Machinery and Materials, Daejun, Zip: 305-343 (Korea, Republic of)

    2008-08-30

    We developed and characterized a new laser bonding process with a nano adhesive layer for transparent materials. The adhesive is spin-coated on a glass substrate and cured locally with a focused laser beam. The minimum viscosity of the adhesive is very low, so that a thin layer only a few hundred nanometers thick can be coated on a cover substrate. Laser irradiation from a Nd:YAG laser system with a wavelength of 1064 nm is employed as the curing source for the localized nano layer bonding process. The measured thickness of the bonding layer is in the range of 400 nm to 3 {mu}m. This process can be applied to the nano or micro bonding of various transparent systems such as flat panel displays, biochips, and heat-sensitive microelectronics. We present experimental results and discuss the process characteristics.

  16. Observation of Temperature Chaos in Mesoscopic Spin Glasses

    Science.gov (United States)

    Guchhait, Samaresh

    Temperature Chaos (TC) results from a change in temperature for spin glasses (SG), polymers, and other glassy materials. When the temperature is changed, TC means that the new state has no memory of the preparation of the initial state. TC was predicted long ago [PRL 48, 767 (1982)]. However, ``An experimental measurement of TC is still missing'' [EPL 103, 67003 (2013)]. One reason for this is the question of length scale. In the thermodynamic limit, even an infinitesimal temperature change, ΔT , will create a chaotic condition. However, by working at the mesoscale, one can establish a length scale sufficiently small to exhibit reversible behavior before crossing over to chaotic behavior as the temperature change increases. Observation of TC is possible because, on reasonable laboratory time scales, the SG correlation length can grow to the size of the thickness of the film, L. The lower critical dimension for a SG is ~ 2 . 5 , so that the thin film SG crosses over to a glass temperature Tg = 0 . However, there remains quasi-equilibrium SG states with length scales calculated TC critical exponent, the range of ΔT for reversible behavior is calculated and is in very good agreement with the measured range. This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Science and Engineering under Award DE-SC0013599.

  17. Nonequilibrium relaxation study of Ising spin glass models

    Science.gov (United States)

    Ozeki, Yukiyasu; Ito, Nobuyasu

    2001-07-01

    As an analysis of equilibrium phase transitions, the nonequilibrium relaxation method is extended to the spin glass (SG) transition. The +/-J Ising SG model is analyzed for three-dimensional (cubic) lattices up to the linear size of L=127 and for four-dimensional (hypercubic) lattice up to L=41. These sizes of systems are quite large as compared with those calculated, so far, by equilibrium simulations. As a dynamical order parameter, we calculate the clone correlation function (CCF) Q(t,tw)≡[F], which is a spin correlation of two replicas produced after the waiting time tw from a simple starting state. It is found that the CCF shows an exponential decay in the paramagnetic phase, and a power-law decay after aginglike development (t>>tw) in the SG phase. This provides a reliable upper bound of the transition temperature Tg. It is also found that a scaling relation, Q(t,tw)=t-λqwq¯(t/tw), holds just around the transition point providing the lower bound of Tg. Together with these two bounds, we propose a new dynamical way for the estimation of Tg from much larger systems. In the SG phase, the power-law behavior of the CCF for t>>tw suggests that the SG phase in short-range Ising models has a rugged phase space.

  18. Quantum spin-glass transition in the two-dimensional electron gas

    Indian Academy of Sciences (India)

    Subir Sachdev

    2002-02-01

    We discuss the possibility of spin-glass order in the vicinity of the unexpected metallic state of the two-dimensional electron gas in zero applied magnetic field. An average ferromagnetic moment may also be present, and the spin-glass order then resides in the plane orthogonal to the ferromagnetic moment. We argue that a quantum transition involving the destruction of the spin-glass order in an applied in-plane magnetic field offers a natural explanation of some features of recent magnetoconductance measurements. We present a quantum field theory for such a transition and compute its mean field properties.

  19. Spin glass models from the point of view of spin distributions

    CERN Document Server

    Panchenko, Dmitry

    2010-01-01

    In many spin glass models, due to the symmetry between sites, any limiting joint distribution of spins under the annealed Gibbs measure admits the Aldous-Hoover representation encoded by a function $\\sigma: [0,1]^4\\to\\{-1,+1\\}$ and one can think of this function as a generic functional order parameter of the model. In a class of diluted models and in the Sherrington-Kirkpatrick model, we introduce novel perturbations of the Hamiltonians that yield certain invariance and self-consistency equations for this generic functional order parameter and we use these invariance properties to obtain representations for the free energy in terms of $\\sigma$. In the setting of the Sherrington-Kirkpatrick model the self-consistency equations imply that the joint distribution of spins is determined by the joint distributions of the overlaps and we give an explicit formula for $\\sigma$ under the Parisi ultrametricity hypothesis. In addition, we discuss some connections with the Ghirlanda-Guerra identities and stochastic stabil...

  20. Exchange bias effect in spin glass CoCr2O4 nanoparticles

    Science.gov (United States)

    Zhu, Changming; Tian, Zhaoming; Wang, Liguang; Yuan, Songliu

    2015-11-01

    CoCr2O4 nanoparticles are about 5.4 nm in diameter synthesized by a hydrothermal technique. Magnetization measurements reveal that the nanoparticles exhibit a spin glass behavior below glass transition temperature. Signature of memory effect is clear in reheating curve where the step-like shape increasing with the increase of temperature is recovered after cooling process. Magnetic relaxation is performed to prove memory effect. Ageing effect is also detected in CoCr2O4 nanoparticles to verify the spin glass behavior. As temperature decreases to 5 K, which is far below the glass transition temperature, exchange bias effect can be observed clearly accompanied with a shift in field-cooled hysteresis loop. As particle size decreases to 5.4 nm, spin glass behavior appears due to the increased spin disorder effect. The spin glass phase providing a pinning force from some frozen spins to the rotatable spins gives the key to explain the exchange bias effects.

  1. Physical Properties of AR-Glass Fibers in Continuous Fiber Spinning Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ji-Sun; Lee, MiJai; Lim, Tae-Young; Lee, Youngjin; Jeon, Dae-Woo; Kim, Jin-Ho [Korea Institute of Ceramic Engineering and Technology, Jinju (Korea, Republic of); Hyun, Soong-Keun [Inha University, Incheon (Korea, Republic of)

    2017-04-15

    In this study, a glass fiber is fabricated using a continuous spinning process from alkali resistant (AR) glass with 4 wt%zirconia. In order to confirm the melting properties of the marble glass, the raw material is placed into a Pt crucible and melted at 1650 ℃ for 2 h, and then annealed. In order to confirm the transparency of the clear marble glass, the visible transmittance is measured and the fiber spinning condition is investigated by using high temperature viscosity measurements. A change in the diameter is observed according to the winding speed in the range of 100–900 rpm; it is also verified as a function of the fiberizing temperature in the range of 1200–1260 ℃. The optimum winding speed and spinning temperature are 500 rpm and 1240 ℃, respectively. The properties of the prepared spinning fiber are confirmed using optical microscope, tensile strength, modulus, and alkali-resistant tests.

  2. Spin glass in a field: a new zero-temperature fixed point in finite dimensions.

    Science.gov (United States)

    Angelini, Maria Chiara; Biroli, Giulio

    2015-03-06

    By using real-space renormalization group (RG) methods, we show that spin glasses in a field display a new kind of transition in high dimensions. The corresponding critical properties and the spin-glass phase are governed by two nonperturbative zero-temperature fixed points of the RG flow. We compute the critical exponents and discuss the RG flow and its relevance for three-dimensional systems. The new spin-glass phase we discovered has unusual properties, which are intermediate between the ones conjectured by droplet and full replica symmetry-breaking theories. These results provide a new perspective on the long-standing debate about the behavior of spin glasses in a field.

  3. Some peculiarities in the behavior of non-Ising spin glasses

    Science.gov (United States)

    Tareyeva, E. E.; Schelkacheva, T. I.; Chtchelkatchev, N. M.

    2015-03-01

    This paper is a review. We outline the main directions in the modern theory of spin glasses. The main content is based on our recent papers, devoted to studying replica symmetry breaking in non-Ising spin glasses. Studying a series of generalized models showed a certain uniformity of the behavior of these generalized spin glasses. Essentially, we observe a significant difference between their behavior and the behavior of the known systems with random couplings of Ising spins—the Sherrington-Kirkpatrick model and the corresponding p-spin model. We find the bifurcation point for the solution with the first replica symmetry breaking, study the form and stability of the solution near the bifurcation point, and show in which cases the transition to the glass state occurs continuously and in which cases, with a jump of the order parameters.

  4. Trilayer Resist Processing Using Spin-On Glass Intermediate Layers

    Science.gov (United States)

    Gupta, Satish K.; Audain, Carver G.

    1984-05-01

    Of the many multilayer resist processes reported in recent years, the trilayer (RIE) resist process has emerged as the most versatile approach capable of defining high aspect ratio features in the micron to submicron regime using either optical, X-ray, or e-beam imaging. However, the relative complexity of the technique has impeded its widespread use in production. Implementation of trilayer resist pro-cessing would be greatly facilitated if spin-on glass (SOG) films were employed as the intermediate etch-mask (barrier) layer in place of the traditional sputtered or plasma deposited inorganic films. Allied Chemical's ACCUGLASS" 103 and ACCUGLASS" Ti-900 are SOG materials designed for use in trilayer resist processing. Cured films of 103 SOG are Si02-like while those from Ti-900 SOG are Ti02-like. In this paper, the properties of these SOG films and their use in trilayer processing are described. Results are presented for several trilayer resist processes carried out employing the SOG barrier layers and two new planarizing sublayer materials.

  5. Practical engineering of hard spin-glass instances

    Science.gov (United States)

    Marshall, Jeffrey; Martin-Mayor, Victor; Hen, Itay

    2016-07-01

    Recent technological developments in the field of experimental quantum annealing have made prototypical annealing optimizers with hundreds of qubits commercially available. The experimental demonstration of a quantum speedup for optimization problems has since then become a coveted, albeit elusive goal. Recent studies have shown that the so far inconclusive results, regarding a quantum enhancement, may have been partly due to the benchmark problems used being unsuitable. In particular, these problems had inherently too simple a structure, allowing for both traditional resources and quantum annealers to solve them with no special efforts. The need therefore has arisen for the generation of harder benchmarks which would hopefully possess the discriminative power to separate classical scaling of performance with size from quantum. We introduce here a practical technique for the engineering of extremely hard spin-glass Ising-type problem instances that does not require "cherry picking" from large ensembles of randomly generated instances. We accomplish this by treating the generation of hard optimization problems itself as an optimization problem, for which we offer a heuristic algorithm that solves it. We demonstrate the genuine thermal hardness of our generated instances by examining them thermodynamically and analyzing their energy landscapes, as well as by testing the performance of various state-of-the-art algorithms on them. We argue that a proper characterization of the generated instances offers a practical, efficient way to properly benchmark experimental quantum annealers, as well as any other optimization algorithm.

  6. Mean field spin glasses treated with PDE techniques

    Science.gov (United States)

    Barra, Adriano; Del Ferraro, Gino; Tantari, Daniele

    2013-07-01

    Following an original idea of Guerra, in these notes we analyze the Sherrington-Kirkpatrick model from different perspectives, all sharing the underlying approach which consists in linking the resolution of the statistical mechanics of the model (e.g. solving for the free energy) to well-known partial differential equation (PDE) problems (in suitable spaces). The plan is then to solve the related PDE using techniques involved in their native field and lastly bringing back the solution in the proper statistical mechanics framework. Within this strand, after a streamlined test-case on the Curie-Weiss model to highlight the methods more than the physics behind, we solve the SK both at the replica symmetric and at the 1-RSB level, obtaining the correct expression for the free energy via an analogy to a Fourier equation and for the self-consistencies with an analogy to a Burger equation, whose shock wave develops exactly at critical noise level (triggering the phase transition). Our approach, beyond acting as a new alternative method (with respect to the standard routes) for tackling the complexity of spin glasses, links symmetries in PDE theory with constraints in statistical mechanics and, as a novel result from the theoretical physics perspective, we obtain a new class of polynomial identities (namely of Aizenman-Contucci type, but merged within the Guerra's broken replica measures), whose interest lies in understanding, via the recent Panchenko breakthroughs, how to force the overlap organization to the ultrametric tree predicted by Parisi.

  7. Effect of the metal-insulator transition on the spin-glass interaction

    Science.gov (United States)

    Hauser, J. J.; Felder, R. J.; Blitzer, L. D.

    1986-03-01

    The effect of the metal-insulator transition on the spin-glass interaction was studied by measuring the magnetic properties of (MnSi)O X as a function of oxygen content X. As X varies from 0 to 3.6 one changes from a metallic to an insulating spin-glass. The transition at X ≲ 1 is marked by a sharp decrease in the susceptibility and a change of the Curie-Weiss temperature (θ) from ferromagnetic to antiferromagnetic.

  8. Spin-Glass-Ferromagnetic Multicritical Point in Amorphous Fe-Mn Alloys

    Science.gov (United States)

    Salamon, M. B.; Rao, K. V.; Chen, H. S.

    1980-03-01

    The ac susceptibility of a sequence of amorphous Fe-Mn alloys shows lines of both spin-glass and ferromagnetic transitions. A detailed scaling-law analysis, treating the common point on the two magnetic phase boundaries as a multicritical point, verifies the scaling hypothesis and yields multicritical, spin-glass, and crossover exponents. The observed behavior compares quite will with position-space renormalization results.

  9. The three-dimensional Edwards-Anderson spin glass in an external magnetic field

    Science.gov (United States)

    Yllanes, David; Janus Collaboration

    2014-03-01

    Spin glasses are a longstanding model for the sluggish dynamics that appears at the glass transition. However, in order for spin glasses to be a faithful model for general glassy physics, we need to introduce an external magnetic field to eliminate their time-reversal symmetry. Unfortunately, little is known about the critical behavior of a spin glass in a field in three spatial dimensions. We have carried out a dynamical study combining equilibrium and non-equilibrium data. In particular, using the Janus computer, we have been able to simulate one thousand samples, each with half a million spins, along a time window spanning ten orders of magnitude for several magnetic fields and temperature protocols. Our main conclusion is that the system has a clearly identifiable dynamical transition, which we discuss in terms of different possibilities for the underlying physics (from a thermodynamical spin-glass transition to a mode-coupling crossover). In fact, we are able to make quantitative connections between the Edwards-Anderson spin glass and the physics of supercooled liquids. We also discuss ongoing work in equilibrium from parallel tempering simulations. Supported by the ERC, grant agreement no. 247328.

  10. Spin-On Glass: Materials and Applications in Advanced IC Technologies

    NARCIS (Netherlands)

    Nguyen, Nhu Toan; Nguyen Nhu, Toan

    1999-01-01

    This thesis deals with the study of shallow PN junction formation by dopant diffusion from Spin-On Glass (SOG) for future deep sub-micron BiCMOS technology. With the advantages of no transient enhanced diffusion and no metal contamination, diffusion from highly doped SOG (also called spin-on dopant

  11. Surface spin disorder and spin-glass-like behaviour in manganese-substituted cobalt ferrite nanoparticles

    Science.gov (United States)

    Topkaya, R.; Akman, Ö.; Kazan, S.; Aktaş, B.; Durmus, Z.; Baykal, A.

    2012-10-01

    Manganese-substituted cobalt ferrite nanoparticles coated with triethylene glycol (TREG) have been prepared by the glycothermal reaction. The effect of Mn substitution and coating on temperature-dependent magnetic properties of the TREG-coated Mn x Co1- x Fe2O4 nanoparticles (0.0 ≤ x ≤ 0.8) with size of 5-7 nm has been investigated in the temperature range of 10-300 K in a magnetic field up to 9 T. After the irreversible processes of the magnetic hysteresis curves were completed, the high-field regions of these curves were fitted by using a `law of approach to saturation' to extract the magnetic properties, such as the effective anisotropy constant ( K eff) and the anisotropy field ( H A) etc. High coercive field of 12.6 kOe is observed in pure cobalt ferrite coated with TREG at 10 K. The low temperature unsaturated magnetization behaviour indicates the core-shell structure of the Mn x Co1- x Fe2O4 NPs. Zero-field-cooled (ZFC) and field-cooled (FC) measurements revealed superparamagnetic phase of TREG-coated Mn x Co1- x Fe2O4 nanoparticles at room temperature. The blocking and irreversibility temperatures obtained from ZFC-FC curves decrease at highest Mn concentration ( x = 0.8). The existence of spin-glass-like surface layer with freezing temperature of 215 K was established with the applied field dependence of the blocking temperatures following the de Almeida-Thouless line for the Mn0.6Co0.4Fe2O4 NPs. The shifted hysteresis loops with exchange bias field of 60 Oe and high-field irreversibility up to 60 kOe in FC M- H curve at 10 K show that spin-glass-like surface spins surrounds around ordered core material of the Mn0.6Co0.4Fe2O4 NPs. FMR measurement show that all the TREG-coated Mn x Co1- x Fe2O4 nanoparticles absorb microwave in broad field range of about ten thousands Oe. The spectra for all the samples have broad linewidth because of angular distributions of easy axis and internal fields of nanoparticles.

  12. Surface spin disorder and spin-glass-like behaviour in manganese-substituted cobalt ferrite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Topkaya, R., E-mail: rtopkaya@gyte.edu.tr [Gebze Institute of Technology, Department of Physics (Turkey); Akman, Oe. [Sakarya University, Department of Physics (Turkey); Kazan, S.; Aktas, B. [Gebze Institute of Technology, Department of Physics (Turkey); Durmus, Z.; Baykal, A. [Fatih University, Department of Chemistry (Turkey)

    2012-10-15

    Manganese-substituted cobalt ferrite nanoparticles coated with triethylene glycol (TREG) have been prepared by the glycothermal reaction. The effect of Mn substitution and coating on temperature-dependent magnetic properties of the TREG-coated Mn{sub x}Co{sub 1-x}Fe{sub 2}O{sub 4} nanoparticles (0.0 {<=} x {<=} 0.8) with size of {approx}5-7 nm has been investigated in the temperature range of 10-300 K in a magnetic field up to 9 T. After the irreversible processes of the magnetic hysteresis curves were completed, the high-field regions of these curves were fitted by using a 'law of approach to saturation' to extract the magnetic properties, such as the effective anisotropy constant (K{sub eff}) and the anisotropy field (H{sub A}) etc. High coercive field of 12.6 kOe is observed in pure cobalt ferrite coated with TREG at 10 K. The low temperature unsaturated magnetization behaviour indicates the core-shell structure of the Mn{sub x}Co{sub 1-x}Fe{sub 2}O{sub 4} NPs. Zero-field-cooled (ZFC) and field-cooled (FC) measurements revealed superparamagnetic phase of TREG-coated Mn{sub x}Co{sub 1-x}Fe{sub 2}O{sub 4} nanoparticles at room temperature. The blocking and irreversibility temperatures obtained from ZFC-FC curves decrease at highest Mn concentration (x = 0.8). The existence of spin-glass-like surface layer with freezing temperature of 215 K was established with the applied field dependence of the blocking temperatures following the de Almeida-Thouless line for the Mn{sub 0.6}Co{sub 0.4}Fe{sub 2}O{sub 4} NPs. The shifted hysteresis loops with exchange bias field of 60 Oe and high-field irreversibility up to 60 kOe in FC M-H curve at 10 K show that spin-glass-like surface spins surrounds around ordered core material of the Mn{sub 0.6}Co{sub 0.4}Fe{sub 2}O{sub 4} NPs. FMR measurement show that all the TREG-coated Mn{sub x}Co{sub 1-x}Fe{sub 2}O{sub 4} nanoparticles absorb microwave in broad field range of about ten thousands Oe. The spectra for all the

  13. Aneesur Rahman Prize for Computational Physics Talk: Numerical Simulations of Spin Glasses and Related Systems

    Science.gov (United States)

    Young, A. Peter

    2009-03-01

    Systems with disorder and ``frustration'' occur in many branches of science. There has been considerable effort to understand one such type of system, known as the ``spin glass'', because it can be probed in fine detail experimentally by applying a magnetic field, and because it can be modeled by simple-looking Hamiltonians which are amenable to numerical simulation. Analytical work is very difficult and has been carried out mainly on models with unphysical features such as infinite-range interactions. Hence, much of what we know about spin glasses and related systems comes from numerical simulations on simplified models. In this talk I will describe some of the difficulties in performing reliable spin glass simulations. Then I will discuss several questions concerning phase transitions in spin glasses and related systems that have been addressed by simulations in recent years including (i) whether there is universality, (ii) whether there is a ``vortex glass'' transition in a disordered type-II superconductor in a magnetic field, (iii) whether ``chiralities'' play a crucial role in Heisenberg spin glasses, and (iv) whether there is a line of transitions (AT line) in a magnetic field.

  14. Elemental analysis and magnetism of hydronium jarosites-model kagome antiferromagnets and topological spin glasses

    Energy Technology Data Exchange (ETDEWEB)

    Wills, A S; Bisson, W G, E-mail: a.s.wills@ucl.ac.uk [Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom)

    2011-04-27

    The jarosites are the most studied examples of kagome antiferromagnets. Research into them has inspired new directions in magnetism, such as the role of the Dzyaloshinsky-Moriya interaction in symmetry breaking, kagome spin ice, and whether spin glass-like phases can exist in the disorder-free limit. This last point is based around the observation of unconventional thermodynamic and kinetic responses in hydronium jarosite, H{sub 3}OFe{sub 3}(SO{sub 4}){sub 2}(OH){sub 6}, that have led to its classification as a 'topological' spin glass, reflecting the defining role that the underlying geometry of the kagome lattice plays in the formation of the spin glass state. In this paper we explore one of the fundamental questions concerning the frustrated magnetism in hydronium jarosite: whether the spin glass phase is the result of chemical disorder and concomitant randomness in the exchange interactions. Confirming previous crystallographic studies, we use elemental analysis to show that the nature of the low temperature magnetic state is not a simple function of chemical disorder and provide evidence to support the hypothesis that anisotropies drive the spin glass transition.

  15. Elemental analysis and magnetism of hydronium jarosites--model kagome antiferromagnets and topological spin glasses.

    Science.gov (United States)

    Wills, A S; Bisson, W G

    2011-04-27

    The jarosites are the most studied examples of kagome antiferromagnets. Research into them has inspired new directions in magnetism, such as the role of the Dzyaloshinsky-Moriya interaction in symmetry breaking, kagome spin ice, and whether spin glass-like phases can exist in the disorder-free limit. This last point is based around the observation of unconventional thermodynamic and kinetic responses in hydronium jarosite, H(3)OFe(3)(SO(4))(2)(OH)(6), that have led to its classification as a 'topological' spin glass, reflecting the defining role that the underlying geometry of the kagome lattice plays in the formation of the spin glass state. In this paper we explore one of the fundamental questions concerning the frustrated magnetism in hydronium jarosite: whether the spin glass phase is the result of chemical disorder and concomitant randomness in the exchange interactions. Confirming previous crystallographic studies, we use elemental analysis to show that the nature of the low temperature magnetic state is not a simple function of chemical disorder and provide evidence to support the hypothesis that anisotropies drive the spin glass transition.

  16. Low temperature spin-glass-like phases in magnetic nano-granular composites

    KAUST Repository

    Zhang, Bei

    2012-09-01

    It is a common understanding that the dipole-dipole interaction among the magnetic nanoparticles may result in a low-temperature spin-glass phase, which has been evidenced by observation of aging effect and memory effect. However, several studies on the nano-particles systems showed that some of the observed spin-glass-like phenomena could be due to the existence of spin-glasslike shells surrounding the ferrimagnetic cores. Therefore, it is very important to understand that how the dipole-dipole interaction induce the spin-glass phase. In order to address this issue, we have fabricated Co-SiO 2 and Fe-SiO 2 nano-granular thin films and measured the memory effect for them. Spin-glass-like phase has been observed at low temperatures. We found that, after annealing, the size of the clusters increased significantly. Based on a simple model, the dipole-dipole interaction between the clusters must be increased accordingly for the annealed samples. Interestingly, the memory effect is greatly weakened in the annealed films, which strongly suggested that the dipole-dipole interaction may not be the major factor for the formation of the low-temperature spin-glass-like phase. Copyright © 2012 American Scientific Publishers All rights reserved.

  17. Classical spin glass system in external field with taking into account relaxation effects

    Science.gov (United States)

    Gevorkyan, A. S.; Abajyan, H. G.

    2013-08-01

    We study statistical properties of disordered spin systems under the influence of an external field with taking into account relaxation effects. For description of system the spatial 1D Heisenberg spin-glass Hamiltonian is used. In addition, we suppose that interactions occur between nearest-neighboring spins and they are random. Exact solutions which define angular configuration of the spin in nodes were obtained from the equations of stationary points of Hamiltonian and the corresponding conditions for the energy local minimum. On the basis of these recurrent solutions an effective parallel algorithm is developed for simulation of stabile spin-chains of an arbitrary length. It is shown that by way of an independent order of N 2 numerical simulations (where N is number of spin in each chain) it is possible to generate ensemble of spin-chains, which is completely ergodic which is equivalent to full self-averaging of spin-chains' vector polarization. Distributions of different parameters (energy, average polarization by coordinates, and spin-spin interaction constant) of unperturbed system are calculated. In particular, analytically is proved and numerically is shown, that for the Heisenberg nearest-neighboring Hamiltonian model, the distribution of spin-spin interaction constants as opposed to widely used Gauss-Edwards-Anderson distribution satisfies Levy alpha-stable distribution law. This distribution is nonanalytic function and does not have variance. In the work we have in detail studied critical properties of an ensemble depending on value of external field parameters (from amplitude and frequency) and have shown that even at weak external fields the spin-glass systemis strongly frustrated. It is shown that frustrations have fractal behavior, they are selfsimilar and do not disappear at scale decreasing of area. By the numerical computation is shown that the average polarization of spin-glass on a different coordinates can have values which can lead to

  18. CALL FOR PAPERS: Special issue on Spin Glasses

    Science.gov (United States)

    Coolen, Ton; Nishimori, Hidetoshi; Sourlas, Nicolas; Wong, Michael

    2007-10-01

    This is a call for contributions to a special issue of Journal of Physics A: Mathematical and Theoretical dedicated to the subject of the conference `Viewing The World Through Spin Glasses', in honour of David Sherrington on the occasion of his 65th birthday, 31 August-1 September 2007 (http://www.nottingham.ac.uk/\\verb.~.ppzjpg/DS2007/). Invited speakers and participants at that meeting and other researchers working in the field are invited to submit a research paper to this issue. The Editorial Board has invited Ton Coolen, Hidetoshi Nishimori, Nicolas Sourlas and Michael Wong to serve as Guest Editors for the special issue. Their criteria for acceptance of contributions are as follows: •The subject of the paper should relate to the subject of the conference (see the website of the conference http://www.nottingham.ac.uk/\\verb.~.ppzjpg/DS2007/). •Contributions will be refereed and processed according to the usual procedure of the journal. •Conference papers may be based on already published work but should either contain significant additional new results and/or insights or give a survey of the present state of the art, a critical assessment of the present understanding of a topic, and a discussion of open problems. •Papers submitted by non-participants should be original and contain substantial new results. The guidelines for the preparation of contributions are the following: •The DEADLINE for submission of contributions is 1 December 2007. This deadline will allow the special issue to appear in July 2008. •There is a nominal page limit of 16 printed pages per contribution. For papers exceeding this limit, the Guest Editors reserve the right to request a reduction in length. •Further advice on publishing your work in Journal of Physics A: Mathematical and Theoretical may be found at www.iop.org/Journals/jphysa. •Contributions to the special issue should, if possible, be submitted electronically by web upload at www.iop.org/Journals/jphysa or by

  19. Spin-density-wave magnetism in dilute copper-manganese alloys

    Energy Technology Data Exchange (ETDEWEB)

    Lamelas, F.J. [Marquette Univ., Milwaukee, WI (United States). Dept. of Physics; Werner, S.A. [Univ. of Missouri, Columbia, MO (United States). Dept. of Physics; Shapiro, S.M. [Brookhaven National Lab., Upton, NY (United States); Mydosh, J.A. [Kammerlingh Onnes Lab., Leiden (Netherlands)

    1995-02-01

    Elastic neutron-scattering measurements on two samples of Cu alloyed with 1.3% Mn and 0.55% Mn show that the spin-density-wave (SDW) features found in more concentrated alloys persist in the limit of very dilute alloys. These features consist of temperature-dependent incommensurate peaks in magnetic neutron scattering, with positions and strengths which are fully consistent with those in the concentrated alloys. The implications of these measurements are twofold. First, it is clear from this data that SDW magnetic ordering occurs across the entire range of CuMn alloys which have typically been interpreted as spin glasses. Second, the more fundamental significance of this work is the suggestion via extrapolation that a peak in the magnetic susceptibility x(q) occurs in pure copper, at a value of q given by the Fermi-surface diameter 2k{sub F}.

  20. Replica exchange Monte Carlo simulations of the ising spin glass: Static and dynamic properties

    Science.gov (United States)

    Yucesoy, Burcu

    Spin glasses have been the subject of intense study and considerable controversy for decades, and the low-temperature phase of short-range spin glasses is still poorly understood. Our main goal is to improve our understanding in this area and find an answer to the following question: Are there only a single pair or a countable infinity of pure states in the low temperature phase of the EA spin glass? To that aim we first start by introducing spin glasses and provide a brief history of their research, then proceed to describe our method of simulation, the parallel tempering Monte Carlo algorithm. Next, we present the results of a large-scale numerical study of the equilibrium three-dimensional Edwards-Anderson Ising spin glass with Gaussian disorder. In order to understand how the parallel tempering algorithm works, we measure various static, as well as dynamical quantities, such as the autocorrelation times and round-trip times for the parallel tempering Monte Carlo method. We examine the correlation between static and dynamic observables for ˜ 5000 disorder realizations and up to 1000 spins down to temperatures at 20% of the critical temperature, and our results show that autocorrelation times are directly correlated with the roughness of the free-energy landscape. In the following chapters, the three- and four-dimensional Edwards-Anderson and mean-field Sherrington-Kirkpatrick Ising spin glasses are studied again via large scale Monte Carlo simulations at low temperatures, deep within the spin glass phase. Performing a careful statistical analysis of several thousand independent disorder realizations and using an observable that detects peaks in the overlap distribution, we show that the Sherrington-Kirkpatrick and Edwards-Anderson models have a distinctly different low-temperature behavior. We arrive to the following conclusion: The structure of the spin-glass overlap distribution for the Edwards-Anderson model suggests that its low-temperature phase has only a

  1. Unconventional critical activated scaling of two-dimensional quantum spin glasses

    Science.gov (United States)

    Matoz-Fernandez, D. A.; Romá, F.

    2016-07-01

    We study the critical behavior of two-dimensional short-range quantum spin glasses by numerical simulations. Using a parallel tempering algorithm, we calculate the Binder cumulant for the Ising spin glass in a transverse magnetic field with two different short-range bond distributions, the bimodal and the Gaussian ones. Through an exhaustive finite-size analysis, we show that the cumulant probably follows an unconventional activated scaling, which we interpret as new evidence supporting the hypothesis that the quantum critical behavior is governed by an infinite randomness fixed point.

  2. Cyclic Heating-Annealing and Boltzmann Distribution of Free Energies in a Spin-Glass System

    Institute of Scientific and Technical Information of China (English)

    ZHOU Hai-Jun

    2007-01-01

    Ergodicity of a spin-glass is broken at low temperatures; the system is trapped in one of many ergodic configurational domains. Transitions between different ergodic domains are achievable through a heating-annealing procedure. If this experiment is repeated infinite times, all ergodic configurational domains will be visited with frequences that decreasing exponentially with their free energies. The mean free energy density of a spin-glass system on a random graph is calculated based on this free energy Boltzmann distribution in the present work, by means of the cavity approach.

  3. Structural study of the re-entrant spin-glass behaviour of Fe-Al alloys

    Energy Technology Data Exchange (ETDEWEB)

    Martin Rodriguez, D. [Bragg Institute, Australian Nuclear Science and Technology Organisation, PMB 1, Menai NSW 2234 (Australia)]. E-mail: dmr@ansto.gov.au; Plazaola, F. [Elektrika eta Elektronika Saila, UPV-EHU, 644 P.K., 48080 Bilbao (Spain); Garitaonandia, J.S. [Fisika Aplikatua II Saila, UPV-EHU, 644 P.K., 48080 Bilbao (Spain); Cuello, G.J. [Institute Laue Langevin, 6 rue Jules Horowitz, B.P. 156, 38042 Grenoble (France)

    2007-09-15

    Neutron powder diffraction measurements were performed on Fe{sub 70}Al{sub 30} alloy in order to determine the relationship between the magnetic behaviour and the structural changes observed in this alloy. Results show that the re-entrant spin-glass behaviour is linked with D03 structure. There is a strong correlation between the lattice parameter and the diffraction peak intensity and all the magnetic changes reported in literature can be explained in terms of this relationship. Finally, magnetovolume effects similar to invar effect are reported in the spin-glass phase.

  4. Glass-wool study of laser-induced spin currents en route to hyperpolarized Cs salt

    Science.gov (United States)

    Ishikawa, Kiyoshi

    2011-07-01

    The nuclear spin polarization of optically pumped Cs atoms flows to the surface of Cs hydride in a vapor cell. A fine glass wool lightly coated with the salt helps greatly increase the surface area in contact with the pumped atoms and enhance the spin polarization of the salt nuclei. Even though the glass wool randomly scatters the pump light, the atomic vapor can be polarized with unpolarized light in a magnetic field. The measured enhancement in the salt enables study of the polarizations of light and atomic nuclei very near the salt surface.

  5. Glass-wool study of laser-induced spin currents en route to hyperpolarized Cs salt

    Energy Technology Data Exchange (ETDEWEB)

    Ishikawa, Kiyoshi [Graduate School of Material Science, University of Hyogo, Ako-gun, Hyogo 678-1297 (Japan)

    2011-07-15

    The nuclear spin polarization of optically pumped Cs atoms flows to the surface of Cs hydride in a vapor cell. A fine glass wool lightly coated with the salt helps greatly increase the surface area in contact with the pumped atoms and enhance the spin polarization of the salt nuclei. Even though the glass wool randomly scatters the pump light, the atomic vapor can be polarized with unpolarized light in a magnetic field. The measured enhancement in the salt enables study of the polarizations of light and atomic nuclei very near the salt surface.

  6. Magnetic correlation, excitation and slow dynamics in concentrated spin-glass alloys

    Indian Academy of Sciences (India)

    Kiyoichiro Motoya

    2004-07-01

    Three kinds of neutron scattering experiments have been performed to clarify the role of magnetic clusters on the various properties of re-entrant spin-glasses. The presence of two kinds of spin-wave excitations, the limitations of magnetic phase diagrams and the mechanism of slow dynamics have been discussed based on the results of in-elastic scattering, diffuse scattering and time-resolved small-angle scattering experiments, respectively.

  7. Large-scale Monte Carlo simulations of the isotropic three-dimensional Heisenberg spin glass

    OpenAIRE

    Lee, L W; Young, A. P.

    2007-01-01

    We study the Heisenberg spin glass by large-scale Monte Carlo simulations for sizes up to 32^3, down to temperatures below the transition temperature claimed in earlier work. The data for the larger sizes show more marginal behavior than that for the smaller sizes, indicating the lower critical dimension is close to, and possibly equal to three. We find that the spins and chiralities behave in a quite similar manner.

  8. Spin-glass transition in bond-disordered Heisenberg antiferromagnets coupled with local lattice distortions on a pyrochlore lattice.

    Science.gov (United States)

    Shinaoka, Hiroshi; Tomita, Yusuke; Motome, Yukitoshi

    2011-07-22

    Motivated by puzzling characteristics of spin-glass transitions widely observed in pyrochlore-based frustrated materials, we investigate the effects of coupling to local lattice distortions in a bond-disordered antiferromagnet on the pyrochlore lattice by extensive Monte Carlo simulations. We show that the spin-glass transition temperature T(f) is largely enhanced by the spin-lattice coupling and, furthermore, becomes almost independent of Δ in a wide range of the disorder strength Δ. The critical property of the spin-glass transition is indistinguishable from that of the canonical Heisenberg spin glass in the entire range of Δ. These peculiar behaviors are ascribed to a modification of the degenerate manifold from a continuous to semidiscrete one by spin-lattice coupling.

  9. LABS problem and ground state spin glasses system

    Science.gov (United States)

    Leukhin, A. N.; Bezrodnyi, V. I.; Kozlova, Yu. A.

    2016-12-01

    In our work we demonstrate the new results of an exhaustive search for optimal binary sequences with minimum peak sidelobe (MPS) up to length N=85. The design problem for law autocorrelation binary sequences (LABS) is a notoriously difficult computational problem which is numbered as the problem number 005 in CSPLib. In statistical physics LABS problem can be interrepted as the energy of N iteracting Ising spins. This is a Bernasconi model. Due to this connection to physics we refer a binary sequence as one-dimensional spin lattice. At this assumption optimal binary sequences by merit factor (MF) criteria are the ground-state spin system without disorder which exhibits a glassy regime.

  10. Spin-glass-like ordering of the magnetic moments of interacting nanosized maghemite particles

    DEFF Research Database (Denmark)

    Mørup, Steen; Bødker, Franz; Hendriksen, Peter Vang

    1995-01-01

    measurements of the decay of remanence are much lower. These results are not in accordance with the Néel model for superparamagnetic relaxation, but can be explained by the formation of an ordered spin-glass-like state at low temperatures. At a critical temperature a transition to a superparamagnetic state...

  11. Orbital Dimer Model for the Spin-Glass State in Y2 Mo2 O7

    Science.gov (United States)

    Thygesen, Peter M. M.; Paddison, Joseph A. M.; Zhang, Ronghuan; Beyer, Kevin A.; Chapman, Karena W.; Playford, Helen Y.; Tucker, Matthew G.; Keen, David A.; Hayward, Michael A.; Goodwin, Andrew L.

    2017-02-01

    The formation of a spin glass generally requires that magnetic exchange interactions are both frustrated and disordered. Consequently, the origin of spin-glass behavior in Y2 Mo2 O7 —in which magnetic Mo4 + ions occupy a frustrated pyrochlore lattice with minimal compositional disorder—has been a longstanding question. Here, we use neutron and x-ray pair-distribution function (PDF) analysis to develop a disorder model that resolves apparent incompatibilities between previously reported PDF, extended x-ray-absorption fine structure spectroscopy, and NMR studies, and provides a new and physical explanation of the exchange disorder responsible for spin-glass formation. We show that Mo4 + ions displace according to a local "two-in-two-out" rule on each Mo4 tetrahedron, driven by orbital dimerization of Jahn-Teller active Mo4 + ions. Long-range orbital order is prevented by the macroscopic degeneracy of dimer coverings permitted by the pyrochlore lattice. Cooperative O2 - displacements yield a distribution of Mo-O-Mo angles, which in turn introduces disorder into magnetic interactions. Our study demonstrates experimentally how frustration of atomic displacements can assume the role of compositional disorder in driving a spin-glass transition.

  12. The ground state energy of the mean field spin glass model

    CERN Document Server

    Koukiou, Flora

    2008-01-01

    From the study of a functional equation of Gibbs measures we calculate the limiting free energy of the Sherrington-Kirkpatrick spin glass model at a particular value of (low) temperature. This implies the following lower bound for the ground state energy $\\epsilon_0$ \\[\\epsilon_0\\geq -0.7833...,\\] close to the replica symmetry breaking and numerical simulations values.

  13. Orbital Dimer Model for the Spin-Glass State in Y_{2}Mo_{2}O_{7}.

    Science.gov (United States)

    Thygesen, Peter M M; Paddison, Joseph A M; Zhang, Ronghuan; Beyer, Kevin A; Chapman, Karena W; Playford, Helen Y; Tucker, Matthew G; Keen, David A; Hayward, Michael A; Goodwin, Andrew L

    2017-02-10

    The formation of a spin glass generally requires that magnetic exchange interactions are both frustrated and disordered. Consequently, the origin of spin-glass behavior in Y_{2}Mo_{2}O_{7}-in which magnetic Mo^{4+} ions occupy a frustrated pyrochlore lattice with minimal compositional disorder-has been a longstanding question. Here, we use neutron and x-ray pair-distribution function (PDF) analysis to develop a disorder model that resolves apparent incompatibilities between previously reported PDF, extended x-ray-absorption fine structure spectroscopy, and NMR studies, and provides a new and physical explanation of the exchange disorder responsible for spin-glass formation. We show that Mo^{4+} ions displace according to a local "two-in-two-out" rule on each Mo_{4} tetrahedron, driven by orbital dimerization of Jahn-Teller active Mo^{4+} ions. Long-range orbital order is prevented by the macroscopic degeneracy of dimer coverings permitted by the pyrochlore lattice. Cooperative O^{2-} displacements yield a distribution of Mo-O-Mo angles, which in turn introduces disorder into magnetic interactions. Our study demonstrates experimentally how frustration of atomic displacements can assume the role of compositional disorder in driving a spin-glass transition.

  14. On the dynamics of spin-glass models of neural networks

    Science.gov (United States)

    Jongen, Greetje

    1999-10-01

    In the first part of the thesis we have studied the parallel dynamics of the Q-Ising spin-glass model of an attractor neural network. The pattern retrieval is seen as a dynamical process of the spins in order to arrive at a configuration similar to one of the embedded patterns. The similarity is expressed by order parameters. Using a probabilistic signal-to-noise analysis we have calculated the time evolution of the order parameters for the asymmetrically and symmetrically diluted architectures and the fully connected architecture. For the first one we have obtained a closed-form solution. For the other architectures feedback correlations of the spins prevent such a closed-form solution, but we have developed a recursive scheme determining the complete time evolution of the order parameters, without any approximation. For these symmetric architectures we have also derived equilibrium fixed-point equations under certain conditions on the noise in the system. They are the same as those obtained in the replica-symmetric mean-field theory. In the second part of the thesis we have applied the replica-symmetric mean-field theory to the XY spin glass with coupled dynamics. In such a model both spins and couplings evolve stochastically, according to coupled equations, but on different time scales. We have defined relevant order parameters and derived a phase diagram. The system exhibits two different spin-glass phases: one describing freezing of the spins only, and one describing freezing of both spins and couplings. Finally, we have calculated the de Almeida-Thouless lines indicating replica-symmetry breaking.

  15. Complex spin glass behavior in Ga2-xFexO3

    Science.gov (United States)

    Mahana, Sudipta; Topwal, D.

    2017-03-01

    We report the results of the dc magnetization and ac susceptibility measurements on solid solutions of Ga2-xFexO3 (with x = 0.75, 1.0, and 1.25). Magnetic behavior in this series of compounds could broadly be explained by the molecular-field-approximation of a three-sublattice ferrimagnetic model considering three inequivalent octahedral sites. Analysis of frequency dispersion of ac susceptibility reveals a transition from the cluster-glass-like phase to the spin-glass-like phase with decreasing temperature for the x = 0.75 composition. Mentioned glassy behavior is found to gradually evolve with the composition (x) from the Ising type character to Heisenberg type behavior to unconventional glassy behavior for the x = 1.25 composition. Ga2-xFexO3 can hence serve as an ideal system for modeling complex spin glasses.

  16. Spin-glass like behaviors in La1-xTbxMnO3 perovskite

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    A series of samples of La1-xTbxMnO3 (0≤x≤0.15) are prepared. The static and dynamic magnetizations of La1-xTbxMnO3 have been investigated. The results indicate that the spins with the short-range order are frozen into random direction at low enough temperatures which leads to the samples exhibiting the spin-glass like behavior. It is considered that the spin-glass like behavior originates from the competition between ferromagnetic double exchange among Mn3+ and Mn2+ and antiferromagnetic superex-change among Mn3+ and Mn3+,as well as Tb3+ and Tb3+.

  17. Phase Transition in the Density of States of Quantum Spin Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Erdős, László, E-mail: lerdos@ist.ac.at [IST Austria (Austria); Schröder, Dominik, E-mail: schroeder.dominik@gmail.com [Ludwig-Maximilians-Universität München (Germany)

    2014-12-15

    We prove that the empirical density of states of quantum spin glasses on arbitrary graphs converges to a normal distribution as long as the maximal degree is negligible compared with the total number of edges. This extends the recent results of Keating et al. (2014) that were proved for graphs with bounded chromatic number and with symmetric coupling distribution. Furthermore, we generalise the result to arbitrary hypergraphs. We test the optimality of our condition on the maximal degree for p-uniform hypergraphs that correspond to p-spin glass Hamiltonians acting on n distinguishable spin- 1/2 particles. At the critical threshold p = n{sup 1/2} we find a sharp classical-quantum phase transition between the normal distribution and the Wigner semicircle law. The former is characteristic to classical systems with commuting variables, while the latter is a signature of noncommutative random matrix theory.

  18. 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: kashif.nadeem@iiu.edu.pk [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)

    2016-06-01

    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.

  19. The upper limit of the in-plane spin splitting of Gaussian beam reflected from a glass-air interface

    OpenAIRE

    Wenguo Zhu; Jianhui Yu; Heyuan Guan; Huihui Lu; Jieyuan Tang; Jun Zhang; Yunhan Luo; Zhe Chen

    2017-01-01

    Optical spin splitting has a promising prospect in quantum information and precision metrology. Since it is typically small, many efforts have been devoted to its enhancement. However, the upper limit of optical spin splitting remains uninvestigated. Here, we investigate systematically the in-plane spin splitting of a Gaussian beam reflected from a glass-air interface and find that the spin splitting can be enhanced in three different incident angular ranges: around the Brewster angle, slight...

  20. Persistent entanglement in a class of eigenstates of quantum Heisenberg spin glasses

    Science.gov (United States)

    Kannawadi, Arun; Sharma, Auditya; Lakshminarayan, Arul

    2016-09-01

    The eigenstates of a quantum spin glass Hamiltonian with long-range interaction are examined from the point of view of localisation and entanglement. In particular, low particle sectors are examined and an anomalous family of eigenstates is found that is more delocalised but also has larger inter-spin entanglement. These are then identified as particle-added eigenstates from the one-particle sector. This motivates the introduction and the study of random promoted two-particle states, and it is shown that they may have large delocalisation such as generic random states and scale exactly like them. However, the entanglement as measured by two-spin concurrence displays different scaling with the total number of spins. This shows how for different classes of complex quantum states entanglement can be qualitatively different even if localisation measures such as participation ratio are not.

  1. Distribution and localization of the harmonic magnon modes in a one-dimensional Heisenberg spin glass

    Science.gov (United States)

    Boukahil, A.; Huber, D. L.

    1989-09-01

    The harmonic magnon modes in a one-dimensional Heisenberg spin glass having nearest-neighbor exchange interactions of fixed magnitude and random sign are investigated. The Lyapounov exponent is calculated for chains of 107-108 spins over the interval 0<=ω<=4J. In the low-frequency regime, ω<~0.1J, an anomalous behavior for the density of states ρ(ω)~ω-1/3 is established, consistent with earlier results obtained by Stinchcombe and Pimentel using transfer-matrix techniques; at higher frequencies, gaps appear in the spectrum. At low frequencies, the localization length diverges as ω-2/3. A formal connection is established between the spin glass and the one-dimensional discretized Schrödinger equation. By making use of the connection, it is shown that the theory of Derrida and Gardner, which was developed for weak potential disorder, can account quantitatively for the distribution and localization of the low-frequency magnon modes in the spin-glass model.

  2. Spin-glass freezing in a Ni-vermiculite intercalation compound.

    Science.gov (United States)

    Marcos, C; Argüelles, A; Khainakov, S A; Rodríguez Fernández, J; Blanco, J A

    2012-08-29

    We report on the magnetic properties of a Ni(2+)-vermiculite intercalation compound from Santa Olalla, Huelva (Spain). This modified vermiculite was studied by means of DC and AC magnetic measurements. The existence of two maxima in magnetic susceptibility below 10 K was interpreted in terms of the Cole-Cole formalism as being due to spin-glass freezing in this material. The temperature, frequency and external magnetic field dependences of these anomalies located at temperatures around 2-3 K and 8-10 K in the imaginary part of the magnetic susceptibility, χ″, seem to suggest the existence of spin-relaxation phenomena between the magnetic moments of the Ni(2+) ions. A dynamic study of the relaxation processes associated with these phenomena considering the Cole-Cole formalism allows us to interpret the anomaly found at 2-3 K according to a law of activated dynamics, obtaining values for the critical exponent, ψν < 1, characteristic of a d = 2 spin-glass-like system, while the maximum observed in χ″ at 8-10 K can be described by means of a law of standard dynamics with a value of the exponent z of around 5, representative of a d = 3 spin-glass-like system.

  3. Competing antiferromagnetic and spin-glass phases in a hollandite structure

    Science.gov (United States)

    Crespo, Y.; Andreanov, A.; Seriani, N.

    2013-07-01

    We introduce a simple lattice model with Ising spins as a zeroth-order approximation of the hollandite-type magnetic compounds. We argue that geometrical frustration of the lattice in combination with nearest-neighbor antiferromagnetic (AFM) interactions are responsible for the appearance of a spin-glass phase in presence of disorder. We investigate this system numerically using parallel tempering. The model reproduces magnetic transitions present in some oxides with hollandite structure and displays a rich phenomenology: in the absence of disorder we have identified five different ground states, depending on the relative strength and sign of the interactions: one ferromagnetically ordered, three antiferromagnetically ordered, and one disordered, macroscopically degenerate ground state. Remarkably, for the sets of AFM couplings having an AFM ground state in the clean system, there exists a critical value of the disorder above which the ground state becomes a spin glass while maintaining all the couplings antiferromagnetically. This model presents this kind of transition with nearest-neighbor frustrated AFM interactions. We argue that this model is useful for understanding the relation between AFM coupling, disorder, and appearance of spin-glass phases.

  4. Effect of modularity on the Glauber dynamics of the dilute spin glass model

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jeong-Man [The Catholic University of Korea, Bucheon (Korea, Republic of)

    2014-11-15

    We study the Glauber dynamics of the dilute, infinite-ranged spin glass model, the so-called dilute Sherrington-Kirkpatrick (dSK) model. The dSK model has sparse couplings and can be classified by the modularity (M) of the coupling matrix. We investigate the effect of the modularity on the relaxation dynamics starting from a random initial state. By using the Glauber dynamics and the replica method, we derive the relaxation dynamics equations for the magnetization (m) and the energy per spin (r), in addition to the equation for the spin glass order parameter (q{sub α}β). In the replica symmetric (RS) analysis, we find that there are two solutions for the RS spin glass order parameter (q): q = 0 which is stable for r < 1/2 and q = (-1+4r{sup 2})/(32r{sup 4}) which is stable for r > 1/2 in the non-modular system and q = 0 which is stable for r < 1/ SQRT(8) and q = (-1+8r{sup 2})/(128r{sup 4}) which is stable for r > 1/ SQRT(8) in the completely modular system. By substituting the proper q values into the equations for r, we find that the relaxation dynamics of r depends on the modularity, M. These results suggest that, in the context of evolutionary theory, the modularity may emerge spontaneously in the point-mutation-only framework (Glauber dynamics) under a changing environment.

  5. Effect of modularity on the Glauber dynamics of the dilute spin glass model

    Science.gov (United States)

    Park, Jeong-Man

    2014-11-01

    We study the Glauber dynamics of the dilute, infinite-ranged spin glass model, the so-called dilute Sherrington-Kirkpatrick (dSK) model. The dSK model has sparse couplings and can be classified by the modularity ( M) of the coupling matrix. We investigate the effect of the modularity on the relaxation dynamics starting from a random initial state. By using the Glauber dynamics and the replica method, we derive the relaxation dynamics equations for the magnetization ( m) and the energy per spin ( r), in addition to the equation for the spin glass order parameter ( q αβ ). In the replica symmetric (RS) analysis, we find that there are two solutions for the RS spin glass order parameter ( q): q = 0which is stable for r 1/2 in the non-modular system and q = 0 which is stable for r 1/ in the completely modular system. By substituting the proper q values into the equations for r, we find that the relaxation dynamics of r depends on the modularity, M. These results suggest that, in the context of evolutionary theory, the modularity may emerge spontaneously in the point-mutation-only framework (Glauber dynamics) under a changing environment.

  6. Finite size scaling study of dynamical phase transitions in two dimensional models: ferromagnet, symmetric and non symmetric spin glasses

    Energy Technology Data Exchange (ETDEWEB)

    Neumann, A.U.; Derrida, B.

    1988-10-01

    We study the time evolution of two configurations submitted to the same thermal noise for several two dimensional models (Ising ferromagnet, symmetric spin glass, non symmetric spin glass). For all these models, we find a non zero critical temperature above which the two configurations always meet. Using finite size scaling ideas, we determine for these three models this dynamical phase transition and some of the critical exponents. For the ferromagnet, the transition T/sub c/ approx. = 2.25 coincides with the Curie temperature whereas for the two spin glass models +- J distribution of bonds) we obtain T/sub c/ approx. = 1.5-1.7.

  7. Comparison of Ising spin glass noise to flux and inductance noise in SQUIDs.

    Science.gov (United States)

    Chen, Zhi; Yu, Clare C

    2010-06-18

    Recent experiments implicate spins on the surface of metals as the source of flux and inductance noise in SQUIDs. We present Monte Carlo simulations of 2D and 3D Ising spin glasses that produce magnetization noise S(M) consistent with flux noise. At low frequencies S(M) is a maximum at the critical temperature T(C) in three dimensions, implying that flux noise should be a maximum at T(C). The second spectra of the magnetization noise and the noise in the susceptibility are consistent with experimentally measured SQUID inductance noise.

  8. Correlations between the dynamics of parallel tempering and the free-energy landscape in spin glasses

    Science.gov (United States)

    Yucesoy, Burcu; Machta, Jonathan; Katzgraber, Helmut G.

    2013-01-01

    We present the results of a large-scale numerical study of the equilibrium three-dimensional Edwards-Anderson Ising spin glass with Gaussian disorder. Using parallel tempering (replica exchange) Monte Carlo we measure various static, as well as dynamical quantities, such as the autocorrelation times and round-trip times for the parallel tempering Monte Carlo method. The correlation between static and dynamic observables for 5000 disorder realizations and up to 1000 spins down to temperatures at 20% of the critical temperature is examined. Our results show that autocorrelation times are directly correlated with the roughness of the free-energy landscape.

  9. Replica exchange simulations of the three-dimensional Ising spin glass: static and dynamic properties

    Science.gov (United States)

    Yucesoy, Burcu; Machta, Jonathan; Katzgraber, Helmut G.

    2012-02-01

    We present the results of a large-scale numerical study of the equilibrium three-dimensional Ising spin glass with Gaussian disorder. Using replica exchange (parallel tempering) Monte Carlo, we measure various static, as well as dynamical quantities, such as the autocorrelation times and round-trip times for the replica exchange Monte Carlo method. The correlation between static and dynamic observables for 5000 disorder realizations (N <=10^3 spins) down to very low temperatures (T 0.2Tc) is examined. Our results show that autocorrelation times are directly correlated with the roughness of the free energy landscape. We also discuss the size dependence of several static quantities.

  10. Magnetic surfactants as molecular based-magnets with spin glass-like properties.

    Science.gov (United States)

    Brown, Paul; Smith, Gregory N; Hernández, Eduardo Padrón; James, Craig; Eastoe, Julian; Nunes, Wallace C; Settens, Charles M; Hatton, T Alan; Baker, Peter J

    2016-05-05

    This paper reports the use of muon spin relaxation spectroscopy to study how the aggregation behavior of magnetic surfactants containing lanthanide counterions may be exploited to create spin glass-like materials. Surfactants provide a unique approach to building in randomness, frustration and competing interactions into magnetic materials without requiring a lattice of ordered magnetic species or intervening ligands and elements. We demonstrate that this magnetic behavior may also be manipulated via formation of micelles rather than simple dilution, as well as via design of surfactant molecular architecture. This somewhat unexpected result indicates the potential of using novel magnetic surfactants for the generation and tuning of molecular magnets.

  11. First-order phase transitions in spin-glass models with multiple paramagnetic solutions

    Energy Technology Data Exchange (ETDEWEB)

    Lozza, H.F. [Departamento de Fisica, FCEyN, Universidad de Buenos Aires, Pab. I, Ciudad Universitaria - (1428) Buenos Aires (Argentina)]. E-mail: homero@df.uba.ar

    2004-12-31

    The paramagnetic and the one-step replica-symmetry-breaking spin-glass solutions of a p-spin-glass model in the presence of a transverse field are studied in the neighborhood of the phase transition curve. Two qualitatively different regions are found in the phase diagram. For a transition temperature higher than a certain value Tc, the thermodynamic transition is of second order, otherwise it is of first order with latent heat. The temperature Tc is joined to a point in the phase diagram where a transition between two paramagnetic solutions happens. A discussion about the order of the thermodynamic-phase transition in the quantum random orthogonal model is presented.

  12. First-order phase transitions in spin-glass models with multiple paramagnetic solutions

    Science.gov (United States)

    Lozza, H. F.

    2004-12-01

    The paramagnetic and the one-step replica-symmetry-breaking spin-glass solutions of a p-spin-glass model in the presence of a transverse field are studied in the neighborhood of the phase transition curve. Two qualitatively different regions are found in the phase diagram. For a transition temperature higher than a certain value Tc, the thermodynamic transition is of second order, otherwise it is of first order with latent heat. The temperature Tc is joined to a point in the phase diagram where a transition between two paramagnetic solutions happens. A discussion about the order of the thermodynamic-phase transition in the quantum random orthogonal model is presented.

  13. Optically controlled spin-glasses generated using multi-qubit cavity systems

    CERN Document Server

    Lee, C F; Lee, Chiu Fan; Johnson, Neil F.

    2004-01-01

    Recent advances in nanofabrication and optical control imply that multi-qubit-cavity systems can now be engineered with pre-designed couplings. Here we propose optical realizations of spin-glass systems which exploit these new nanoscale technologies. By contrast with traditional realizations using magnetic solids, phase transition phenomena can now arise in both the matter and radiation subsystems. Moreover the phase transitions are tunable simply by varying the matter-radiation coupling strength.

  14. Typical versus averaged overlap distribution in spin glasses: Evidence for droplet scaling theory

    Science.gov (United States)

    Monthus, Cécile; Garel, Thomas

    2013-10-01

    We consider the statistical properties over disordered samples (J) of the overlap distribution PJ(q) which plays the role of an order parameter in spin glasses. We show that near zero temperature (i) the typical overlap distribution is exponentially small in the central region of -1models in which the notion of length does not exist); (ii) the rescaled variable v=-[lnPJ(q)]/Nθ remains an O(1) random positive variable describing sample-to-sample fluctuations; (iii) the averaged distribution PJ(q)¯ is nontypical and dominated by rare anomalous samples. Similar statements hold for the cumulative overlap distribution IJ(q0)≡∫0q0dqPJ(q). These results are derived explicitly for the spherical mean-field model with θ=1/3, ϕ(q)=1-q2, and the random variable v corresponds to the rescaled difference between the two largest eigenvalues of Gaussian orthogonal ensemble random matrices. Then we compare numerically the typical and averaged overlap distributions for the long-ranged one-dimensional Ising spin glass with random couplings decaying as J(r)∝r-σ for various values of the exponent σ, corresponding to various droplet exponents θ(σ), and for the mean-field Sherrington-Kirkpatrick model (corresponding formally to the σ=0 limit of the previous model). Our conclusion is that future studies on spin glasses should measure the typical values of the overlap distribution Ptyp(q) or of the cumulative overlap distribution Ityp(q0)=elnIJ(q0)¯ to obtain clearer conclusions on the nature of the spin-glass phase.

  15. Dynamical transition in molecular glasses and proteins observed by spin relaxation of nitroxide spin probes and labels

    Science.gov (United States)

    Golysheva, Elena A.; Shevelev, Georgiy Yu.; Dzuba, Sergei A.

    2017-08-01

    In glassy substances and biological media, dynamical transitions are observed in neutron scattering that manifests itself as deviations of the translational mean-squared displacement, , of hydrogen atoms from harmonic dynamics. In biological media, the deviation occurs at two temperature intervals, at ˜100-150 K and at ˜170-230 K, and it is attributed to the motion of methyl groups in the former case and to the transition from harmonic to anharmonic or diffusive motions in the latter case. In this work, electron spin echo (ESE) spectroscopy—a pulsed version of electron paramagnetic resonance—is applied to study the spin relaxation of nitroxide spin probes and labels introduced in molecular glass former o-terphenyl and in protein lysozyme. The anisotropic contribution to the rate of the two-pulse ESE decay, ΔW, is induced by spin relaxation appearing because of restricted orientational stochastic molecular motion; it is proportional to τc, where is the mean-squared angle of reorientation of the nitroxide molecule around the equilibrium position and τc is the correlation time of reorientation. The ESE time window allows us to study motions with τc τc temperature dependence shows a transition near 240 K, which is in agreement with the literature data on . For spin probes of essentially different size, the obtained data were found to be close, which evidences that motion is cooperative, involving a nanocluster of several neighboring molecules. For the dry lysozyme, the τc values below 260 K were found to linearly depend on the temperature in the same way as it was observed in neutron scattering for . As spin relaxation is influenced only by stochastic motion, the harmonic motions seen in ESE must be overdamped. In the hydrated lysozyme, ESE data show transitions near 130 K for all nitroxides, near 160 K for the probe located in the hydration layer, and near 180 K for the label in the protein interior. For this system, the two latter transitions are not

  16. About a solvable mean field model of a Gaussian spin glass

    Science.gov (United States)

    Barra, Adriano; Genovese, Giuseppe; Guerra, Francesco; Tantari, Daniele

    2014-04-01

    In a series of papers, we have studied a modified Hopfield model of a neural network, with learned words characterized by a Gaussian distribution. The model can be represented as a bipartite spin glass, with one party described by dichotomic Ising spins, and the other party by continuous spin variables, with an a priori Gaussian distribution. By application of standard interpolation methods, we have found it useful to compare the neural network model (bipartite) from one side, with two spin glass models, each monopartite, from the other side. Of these, the first is the usual Sherrington-Kirkpatrick model, the second is a spin glass model, with continuous spins and inbuilt highly nonlinear smooth cut-off interactions. This model is an invaluable laboratory for testing all techniques which have been useful in the study of spin glasses. The purpose of this paper is to give a synthetic description of the most peculiar aspects, by stressing the necessary novelties in the treatment. In particular, it will be shown that the control of the infinite volume limit, according to the well-known Guerra-Toninelli strategy, requires in addition one to consider the involvement of the cut-off interaction in the interpolation procedure. Moreover, the control of the ergodic region, the annealed case, cannot be directly achieved through the standard application of the Borel-Cantelli lemma, but requires previous modification of the interaction. This remark could find useful application in other cases. The replica symmetric expression for the free energy can be easily reached through a suitable version of the doubly stochastic interpolation technique. However, this model shares the unique property that the fully broken replica symmetry ansatz can be explicitly calculated. A very simple sum rule connects the general expression of the fully broken free energy trial function with the replica symmetric one. The definite sign of the error term shows that the replica solution is optimal. Then

  17. Antiferromagnetic Ising spin glass competing with BCS pairing interaction in a transverse field

    Science.gov (United States)

    Magalhães, S. G.; Zimmer, F. M.; Kipper, C. J.; Calegari, E. J.

    2006-07-01

    The competition among spin glass (SG), antiferromagnetism (AF) and local pairing superconductivity (PAIR) is studied in a two-sublattice fermionic Ising spin glass model with a local BCS pairing interaction in the presence of an applied magnetic transverse field Γ. In the present approach, spins in different sublattices interact with a Gaussian random coupling with an antiferromagnetic mean J0 and standard deviation J. The problem is formulated in the path integral formalism in which spin operators are represented by bilinear combinations of Grassmann variables. The saddle-point Grand Canonical potential is obtained within the static approximation and the replica symmetric ansatz. The results are analysed in phase diagrams in which the AF and the SG phases can occur for small g (g is the strength of the local superconductor coupling written in units of J), while the PAIR phase appears as unique solution for large g. However, there is a complex line transition separating the PAIR phase from the others. It is second order at high temperature that ends in a tricritical point. The quantum fluctuations affect deeply the transition lines and the tricritical point due to the presence of Γ.

  18. Critical properties of short-range Ising spin glasses on a Wheatstone-bridge hierarchical lattice.

    Science.gov (United States)

    Almeida, Sebastião T O; Nobre, Fernando D

    2015-08-01

    An Ising spin-glass model with nearest-neighbor interactions, following a symmetric probability distribution, is investigated on a hierarchical lattice of the Wheatstone-bridge family characterized by a fractal dimension D≈3.58. The interaction distribution considered is a stretched exponential, which has been shown recently to be very close to the fixed-point coupling distribution, and such a model has been considered lately as a good approach for Ising spin glasses on a cubic lattice. An exact recursion procedure is implemented for calculating site magnetizations, mi=〈Si〉T, as well as correlations between pairs of nearest-neighbor spins, 〈SiSj〉T (〈〉T denote thermal averages), for a given set of interaction couplings on this lattice. From these local magnetizations and correlations, one can compute important physical quantities, such as the Edwards-Anderson order parameter, the internal energy, and the specific heat. Considering extrapolations to the thermodynamic limit for the order parameter, such as a finite-size scaling approach, it is possible to obtain directly the critical temperature and critical exponents. The transition between the spin-glass and paramagnetic phases is analyzed, and the associated critical exponents β and ν are estimated as β=0.82(5) and ν=2.50(4), which are in good agreement with the most recent results from extensive numerical simulations on a cubic lattice. Since these critical exponents were obtained from a fixed-point distribution, they are universal, i.e., valid for any coupling distribution considered.

  19. Nanocomposites of silver nanoparticles embedded in glass nanofibres obtained by laser spinning.

    Science.gov (United States)

    Cabal, Belén; Quintero, Félix; Díaz, Luís Antonio; Rojo, Fernando; Dieste, Oliver; Pou, Juan; Torrecillas, Ramón; Moya, José Serafín

    2013-05-07

    Nanocomposites made of non-woven glass fibres with diameters ranging from tens of nanometers up to several micrometers, containing silver nanoparticles, were successfully fabricated by the laser spinning technique. Pellets of a soda-lime silicate glass containing silver nanoparticles with varying concentrations (5 and 10 wt%) were used as a precursor. The process followed to obtain the silver nanofibres did not agglomerate significantly the metallic nanoparticles, and the average particle size is still lower than 50 nm. This is the first time that glass nanofibres containing silver nanoparticles have been obtained following a process different from electrospinning of a sol-gel, thus avoiding the limitations of this method and opening a new route to composite nanomaterials. Antibacterial efficiency of the nanosilver glass fibres, tested against one of the most common gram negative bacteria, was greater than 99.99% compared to the glass fibres free of silver. The silver nanoparticles are well-dispersed not only on the surface but are also embedded into the uniform nanofibres, which leads to a long lasting durable antimicrobial effect. All these novel characteristics will potentially open up a whole new range of applications.

  20. Nanocomposites of silver nanoparticles embedded in glass nanofibres obtained by laser spinning

    Science.gov (United States)

    Cabal, Belén; Quintero, Félix; Díaz, Luís Antonio; Rojo, Fernando; Dieste, Oliver; Pou, Juan; Torrecillas, Ramón; Moya, José Serafín

    2013-04-01

    Nanocomposites made of non-woven glass fibres with diameters ranging from tens of nanometers up to several micrometers, containing silver nanoparticles, were successfully fabricated by the laser spinning technique. Pellets of a soda-lime silicate glass containing silver nanoparticles with varying concentrations (5 and 10 wt%) were used as a precursor. The process followed to obtain the silver nanofibres did not agglomerate significantly the metallic nanoparticles, and the average particle size is still lower than 50 nm. This is the first time that glass nanofibres containing silver nanoparticles have been obtained following a process different from electrospinning of a sol-gel, thus avoiding the limitations of this method and opening a new route to composite nanomaterials. Antibacterial efficiency of the nanosilver glass fibres, tested against one of the most common Gram negative bacteria, was greater than 99.99% compared to the glass fibres free of silver. The silver nanoparticles are well-dispersed not only on the surface but are also embedded into the uniform nanofibres, which leads to a long lasting durable antimicrobial effect. All these novel characteristics will potentially open up a whole new range of applications.

  1. Observation of spin glass behavior in monoclinic Li{sub 0.33}MnO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Bie, Xiaofei; Wei, Yingjin; Liu, Lina [Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University, Changchun 130012 (China); Nikolowski, Kristian; Ehrenberg, Helmut [Institute for Applied Materials (IAM), Karlsruhe Institute of Technology (KIT), D-76344 Eggenstein-Leopoldshafen (Germany); Chen, Hong [College of Physics, Beihua University, Jilin 132013 (China); Wang, Chunzhong; Chen, Gang [Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University, Changchun 130012 (China); Du, Fei, E-mail: dufei@jlu.edu.cn [Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University, Changchun 130012 (China)

    2013-02-25

    Highlights: Black-Right-Pointing-Pointer The structure of Li{sub 0.33}MnO{sub 2} has been refined with monoclinic phase (space group C2/m). Black-Right-Pointing-Pointer Spin glass has been confirmed by analyzing dc, ac, and time-dependence remanence. Black-Right-Pointing-Pointer Geometrical frustration combined random competition was suggested to be the main cause for spin glass formation. Black-Right-Pointing-Pointer In order to distinguish the spin glass from the superparamagnetism, ac susceptibility under different frequencies is studied. - Abstract: The structure and magnetic properties of Li{sub 0.33}MnO{sub 2} were studied by X-ray diffraction, dc and ac susceptibilities. Li{sub 0.33}MnO{sub 2} belongs to the monoclinic structure with two different Mn sites. The irreversibility and spin freezing behaviors are observed in the dc magnetization curves. The peaks of ac susceptibility display the dependences on the frequency. Both the magnetic relaxation effect and the corresponding analysis confirm a spin glass (SG) transition at low temperature. By evaluating the geometrical frustration parameter, we suggest the spin glass in Li{sub 0.33}MnO{sub 2} originate from the frustration effect combined with the competition among the Mn{sup 3+/4+}-O{sup 2-}-Mn{sup 3+/4+} exchange interaction.

  2. Hydration-induced spin-glass state in a frustrated Na-Mn-O triangular lattice

    Science.gov (United States)

    Bakaimi, Ioanna; Brescia, Rosaria; Brown, Craig M.; Tsirlin, Alexander A.; Green, Mark A.; Lappas, Alexandros

    2016-05-01

    Birnessite compounds are stable across a wide range of compositions that produces a remarkable diversity in their physical, electrochemical, and functional properties. These are hydrated analogs of the magnetically frustrated, mixed-valent manganese oxide structures, with general formula, N axMn O2 . Here we demonstrate that the direct hydration of layered rock-salt type α-NaMn O2 , with the geometrically frustrated triangular lattice topology, yields the birnessite type oxide, N a0.36Mn O2.0.2 H2O , transforming its magnetic properties. This compound has a much-expanded interlayer spacing compared to its parent α-NaMn O2 compound. We show that while the parent α-NaMn O2 possesses a Néel temperature of 45 K as a result of broken symmetry in the M n3 + sublattice, the hydrated derivative undergoes collective spin freezing at 29 K within the M n3 +/M n4 + sublattice. Scaling-law analysis of the frequency dispersion of the ac susceptibility, as well as the temperature-dependent, low-field dc magnetization confirm a cooperative spin-glass state of strongly interacting spins. This is supported by complementary spectroscopic analysis [high-angle annular dark-field scanning transmission electron miscroscopy (TEM), energy-dispersive x-ray spectroscopy, and electron energy-loss spectroscopy] as well as by a structural investigation (high-resolution TEM, x-ray, and neutron powder diffraction) that yield insights into the chemical and atomic structure modifications. We conclude that the spin-glass state in birnessite is driven by the spin frustration imposed by the underlying triangular lattice topology that is further enhanced by the in-plane bond-disorder generated by the mixed-valent character of manganese in the layers.

  3. Spin-exchange interaction between transition metals and metalloids in soft-ferromagnetic metallic glasses

    Science.gov (United States)

    Das, Santanu; Choudhary, Kamal; Chernatynskiy, Aleksandr; Choi Yim, Haein; Bandyopadhyay, Asis K.; Mukherjee, Sundeep

    2016-06-01

    High-performance magnetic materials have immense industrial and scientific importance in wide-ranging electronic, electromechanical, and medical device technologies. Metallic glasses with a fully amorphous structure are particularly suited for advanced soft-magnetic applications. However, fundamental scientific understanding is lacking for the spin-exchange interaction between metal and metalloid atoms, which typically constitute a metallic glass. Using an integrated experimental and molecular dynamics approach, we demonstrate the mechanism of electron interaction between transition metals and metalloids. Spin-exchange interactions were investigated for a Fe-Co metallic glass system of composition [(Co1-x Fe x )0.75B0.2Si0.05]96Cr4. The saturation magnetization increased with higher Fe concentration, but the trend significantly deviated from simple rule of mixtures. Ab initio molecular dynamics simulation was used to identify the ferromagnetic/anti-ferromagnetic interaction between the transition metals and metalloids. The overlapping band-structure and density of states represent ‘Stoner type’ magnetization for the amorphous alloys in contrast to ‘Heisenberg type’ in crystalline iron. The enhancement of magnetization by increasing iron was attributed to the interaction between Fe 3d and B 2p bands, which was further validated by valence-band study.

  4. Spin-glass behaviors in carrier polarity controlled Fe3-xTixO4 semiconductor thin films

    Science.gov (United States)

    Yamahara, H.; Seki, M.; Adachi, M.; Takahashi, M.; Nasu, H.; Horiba, K.; Kumigashira, H.; Tabata, H.

    2015-08-01

    Carrier-type control of spin-glass (cluster spin-glass) is studied in order to engineer basic magnetic semiconductor elements using the memory functions of spin-glass. A key of carrier-polarity control in magnetite is the valence engineering between Fe(II) and Fe(III) that is achieved by Ti(IV) substitution. Single phases of (001)-oriented Fe3-xTixO4 thin films have been obtained on spinel MgAl2O4 substrates by pulsed laser deposition. Thermoelectric power measurements reveal that Ti-rich films (x = 0.8) show p-type conduction, while Ti-poor films (x = 0.6-0.75) show n-type conduction. The systematic Fe(III) reduction to Fe(II) followed by Ti(IV) substitution in the octahedral sublattice is confirmed by the X-ray absorption spectra. All of the Fe3-xTixO4 films (x = 0.6-0.8) exhibit ferrimagnetism above room temperature. Next, the spin-glass behaviors of Ti-rich Fe2.2Ti0.8O4 film are studied, since this magnetically diluted system is expected to exhibit the spin-glass behaviors. The DC magnetization and AC susceptibility measurements for the Ti-rich Fe2.2Ti0.8O4 film reveal the presence of the spin glass phase. Thermal- and magnetic-field-history memory effects are observed and are attributed to the long time-decay nature of remanent magnetization. The detailed analysis of the time-dependent thermoremanent magnetization reveals the presence of the cluster spin glass state.

  5. Avalanches and hysteresis in frustrated superconductors and XY spin-glasses

    Science.gov (United States)

    Sharma, Auditya; Andreanov, Alexei; Mueller, Markus

    2014-03-01

    We study avalanches along the hysteresis loop of long-range interacting spin-glasses with continuous XY symmetry - which serves as a toy model of granular superconductors with long-range and frustrated Josephson couplings. We identify sudden jumps in the T = 0 configurations of the XY phases, as an external field is increased. They are initiated by the softest mode of the inverse susceptibility matrix becoming unstable, which induces an avalanche of phase updates (or spin alignments). We analyze the statistics of these events, and study the correlation between the no n-linear avalanches and the soft mode that initiates them. We find that the avalanches follow the directions of a small fraction of the softest modes of the inverse susceptibility matrix, sim ilarly as was found in avalanches in jammed systems. In contrast to the similar Ising spin-glass (Sherrington-Kirkpatrick) studied previously, we find that avalanches are not distributed with a scale-free power law, but rather have a typical size which scales with the system size.

  6. Dynamics of one-dimensional Heisenberg spin glasses in the high-field limit

    Science.gov (United States)

    Boukahil, A.; Huber, D. L.

    1994-08-01

    This paper reports the results of a study of the distribution and localization of the magnon modes in one-dimensional Heisenberg spin glasses with nearest-neighbor interactions. The analysis is limited to high fields and frequencies near the precession frequency. Both symmetric and asymmetric distributions of exchange interactions of the form P(J)~||J||-α (α<1) are treated in detail. The results of approximate calculations based on the coherent-exchange approximation are shown to be in good agreement with numerical data obtained by applying mode-counting techniques to arrays of 107 spins. Particular emphasis is placed on the qualitative differences in the behavior that arise depending on whether the average values of J-1 and J-2 are zero, nonzero, or infinite.

  7. Constructive interference between disordered couplings enhances multiparty entanglement in quantum Heisenberg spin glass models

    Science.gov (United States)

    Mishra, Utkarsh; Rakshit, Debraj; Prabhu, R.; Sen(De, Aditi; Sen, Ujjwal

    2016-08-01

    Disordered systems form one of the centrestages of research in many body sciences and lead to a plethora of interesting phenomena and applications. A paradigmatic disordered system consists of a one-dimensional array of quantum spin-1/2 particles, governed by the Heisenberg spin glass Hamiltonian with natural or engineered quenched disordered couplings in an external magnetic field. These systems allow disorder-induced enhancement for bipartite and multipartite observables. Here we show that simultaneous application of independent quenched disorders results in disorder-induced enhancement, while the same is absent with individual application of the same disorders. We term the phenomenon as constructive interference and the corresponding parameter stretches as the Venus regions. Interestingly, it has only been observed for multiparty entanglement and is absent for the single- and two-party physical quantities.

  8. Universality and extremal aging for dynamics of spin glasses on sub-exponential time scales

    CERN Document Server

    Arous, G Ben

    2010-01-01

    We consider Random Hopping Time (RHT) dynamics of the Sherrington - Kirkpatrick (SK) model and p-spin models of spin glasses. For any of these models and for any inverse temperature we prove that, on time scales that are sub-exponential in the dimension, the properly scaled clock process (time-change process) of the dynamics converges to an extremal process. Moreover, on these time scales, the system exhibits aging like behavior which we called extremal aging. In other words, the dynamics of these models ages as the random energy model (REM) does. Hence, by extension, this confirms Bouchaud's REM-like trap model as a universal aging mechanism for a wide range of systems which, for the first time, includes the SK model.

  9. Numerical results for the Edwards-Anderson spin-glass model at low temperature

    Science.gov (United States)

    Fernández, Julio F.; Alonso, Juan J.

    2013-04-01

    We have simulated Edwards-Anderson (EA) as well as Sherrington-Kirkpatrick systems of L3 spins. After averaging over large sets of EA system samples of 3≤L≤10, we obtain accurate numbers for distributions p(q) of the overlap parameter q at very low-temperature T. We find p(0)/T→0.233(4) as T→0. This is in contrast with the droplet scenario of spin glasses. We also study the number of mismatched links—between replica pairs—that come with large scale excitations. Contributions from small scale excitations are discarded. We thus obtain for the fractal dimension of outer surfaces of q˜0 excitations in the EA model ds→2.59(3) as T→0. This is in contrast with ds→3 as T→0 that is predicted by mean-field theory for the macroscopic limit.

  10. Universal critical behavior of the two-dimensional Ising spin glass

    Science.gov (United States)

    Fernandez, L. A.; Marinari, E.; Martin-Mayor, V.; Parisi, G.; Ruiz-Lorenzo, J. J.

    2016-07-01

    We use finite size scaling to study Ising spin glasses in two spatial dimensions. The issue of universality is addressed by comparing discrete and continuous probability distributions for the quenched random couplings. The sophisticated temperature dependency of the scaling fields is identified as the major obstacle that has impeded a complete analysis. Once temperature is relinquished in favor of the correlation length as the basic variable, we obtain a reliable estimation of the anomalous dimension and of the thermal critical exponent. Universality among binary and Gaussian couplings is confirmed to a high numerical accuracy.

  11. Spin-glass phase in a neutral network with asymmetric couplings

    Science.gov (United States)

    Kree, R.; Widmaier, D.; Zippelius, A.

    1988-12-01

    The author studies the phase diagram of a neural network model which has learnt with the ADALINE algorithm, starting from tabula non rasa conditions. The resulting synaptic efficacies are not symmetric under an exchange of the pre- and post-synaptic neuron. In contrast to several other models which have been discussed in the literature, he finds a spin-glass phase in the asymmetrically coupled network. The main difference compared with the other models consists of long-ranged Gaussian correlations in the ensemble of couplings.

  12. The pitfalls of planar spin-glass benchmarks: raising the bar for quantum annealers (again)

    Science.gov (United States)

    Mandrà, Salvatore; Katzgraber, Helmut G.; Thomas, Creighton

    2017-09-01

    In an effort to overcome the limitations of random spin-glass benchmarks for quantum annealers, focus has shifted to carefully crafted gadget-based problems whose logical structure typically has a planar topology. Recent experiments on these gadget problems using a commercially available quantum annealer have demonstrated an impressive performance over a selection of commonly used classical optimisation heuristics. Here, we show that efficient classical optimisation techniques, such as minimum-weight-perfect matching, can solve these gadget problems exactly and in polynomial time. We present approaches on how to mitigate this shortcoming of commonly used benchmark problems based on planar logical topologies.

  13. The cumulative overlap distribution function in spin glasses: mean field vs. three dimensions

    Science.gov (United States)

    Yllanes, David; Billoire, Alain; Maiorano, Andrea; Marinari, Enzo; Martin-Mayor, Victor

    2015-03-01

    We use a sample-dependent analysis, based on medians and quantiles, to analyze the behavior of the overlap probability distribution in spin glasses. Using analytical and numerical mean-field results for the Sherrington-Kirkpatrick model, as well as data from toy models, we show that this approach is an effective tool to distinguish the low-temperature behavior of replica symmmetry breaking systems from that expected in the droplet picture. An application of the method to the three-dimensional Edwards-Anderson models shows agreement with the replica symmetry breaking predictions. Supported by ERC Grant No. 247328 and from MINECO (Spain), Contract No. FIS2012-35719-C02.

  14. Electron scattering mechanisms in Cu-Mn films for interconnect applications

    Energy Technology Data Exchange (ETDEWEB)

    Misják, F.; Nagy, K. H.; Radnóczi, G. [Research Centre for Natural Sciences, Hungarian Academy of Sciences, H-1525 Budapest, P.O. Box 49, Hungary, (Hungary); Lobotka, P. [Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava (Slovakia)

    2014-08-28

    Electrical properties and corresponding structural features of Cu-Mn alloy films with potential application as barrier and interconnect layers were studied. Cu-Mn films were deposited by DC magnetron sputtering at room temperature on SiO{sub 2} substrates. Electrical resistivity measurements were made as a function of film composition and temperature. The specific resistivity varies linearly with the Mn content showing a maximum of 205 μΩcm at 80 at. % Mn. The temperature coefficient of resistance (TCR) of all alloy films is low, showing non-metallic conductivity for most compositions. Also a minimum TCR has been observed in the 40–80 at. % Mn range which was attributed to a magnetic transformation around 200–300 K. Electrical resistivity measurements are correlated with the film structure revealed by transmission electron microscopy to clarify the phase regions throughout the composition range. In the 20–40 at. % and 70–80 at. % Mn ranges, two-phase structures were identified, where Cu- or Mn-rich solid solution grains were surrounded by a thin amorphous covering layer. Based on the revealed phase regions and morphologies electron scattering mechanisms in the system were evaluated by combining the Matthiessen's rule and the Mayadas-Schatzkes theory. Grain boundary reflectivity coefficients (r = 0.6–0.8) were calculated from fitting the model to the measurements. The proposed model indicates that, in a binary system, the special arrangement of the two phases results in new scattering mechanisms. The results are of value in optimizing the various parameters needed to produce a suitable barrier layer.

  15. Search for the Heisenberg spin glass on rewired cubic lattices with antiferromagnetic interaction

    Science.gov (United States)

    Surungan, Tasrief

    2016-10-01

    Spin glass (SG) is a typical magnetic system which is mainly characterized by a frozen random spin orientation at low temperatures. Frustration and randomness are considered to be the key ingredients for the existence of SGs. Previously, Bartolozzi et al. [Phys. Rev. B73, 224419 (2006)] found that the antiferromagnetic (AF) Ising spins on scale free network (SFN) exhibited SG behavior. This is purely AF system, a new type of SG different from the canonical one which requires the presence of both FM and AF couplings. In this new system, frustration is purely due to a topological factor and its randomness is brought by irregular connectivity. Recently, it was reported that the AF Heisenberg model on SFN exhibited SG behavior [Surungan et al., JPCS, 640, 012005 (2015)/doi:10.1088/1742-6596/640/1/012005]. In order to accommodate the notion of spatial dimension, we further investigated this type of system by studying an AF Heisenberg model on rewired cubic lattices, constructed by adding one extra bond randomly connecting each spin to one of its next-nearest neighbors. We used Replica Exchange algorithm of Monte Carlo Method and calculated the SG order parameter to search for the existence of SG phase.

  16. Discovery of room-temperature spin-glass behaviors in two-dimensional oriented attached single crystals

    Science.gov (United States)

    Ma, Ji; Chen, Kezheng

    2016-05-01

    In this study, room-temperature spin-glass behaviors were observed in flake-like oriented attached hematite (α-Fe2O3) and iron phosphate hydroxide hydrate (Fe5(PO4)4(OH)3·2H2O) single crystals. Remarkably, their coercivity (HC) values were found to be almost invariable at various given temperatures from 5 to 300 K. The spin topographic map in these flakes was assumed as superparamagnetic (SPM) "islands" isolated by spin glass (SG)-like "bridges". A spin-glass model was then proposed to demonstrate the spin frustration within these "bridges", which were formed by the staggered atomic planes in the uneven surfaces belonging to different attached nanoparticles. Under the spatial limitation and coupling shield of these "bridges", the SPM "islands" were found to be collectively frozen to form a superspin glass (SSG) state below 80 K in weak applied magnetic fields; whereas, when strong magnetic fields were applied, the magnetic coupling of these "islands" would become superferromagnetic (SFM) through tunneling superexchange, so that, these SFM spins could antiferromagnetically couple with the SG-like "bridges" to yield pronounced exchange bias (EB) effect.

  17. Quantum versus classical annealing: insights from scaling theory and results for spin glasses on 3-regular graphs.

    Science.gov (United States)

    Liu, Cheng-Wei; Polkovnikov, Anatoli; Sandvik, Anders W

    2015-04-10

    We discuss an Ising spin glass where each S=1/2 spin is coupled antiferromagnetically to three other spins (3-regular graphs). Inducing quantum fluctuations by a time-dependent transverse field, we use out-of-equilibrium quantum Monte Carlo simulations to study dynamic scaling at the quantum glass transition. Comparing the dynamic exponent and other critical exponents with those of the classical (temperature-driven) transition, we conclude that quantum annealing is less efficient than classical simulated annealing in bringing the system into the glass phase. Quantum computing based on the quantum annealing paradigm is therefore inferior to classical simulated annealing for this class of problems. We also comment on previous simulations where a parameter is changed with the simulation time, which is very different from the true Hamiltonian dynamics simulated here.

  18. Evidence of Non-Mean-Field-Like Low-Temperature Behavior in the Edwards-Anderson Spin-Glass Model

    Science.gov (United States)

    Yucesoy, Burcu; Katzgraber, Helmut G.; Machta, Jonathan

    2013-03-01

    The three and four-dimensional Edwards-Anderson and mean-field Sherrington-Kirkpatrick Ising spin glasses are studied via large-scale Monte Carlo simulations at low temperatures, deep within the spin-glass phase. Performing a careful statistical analysis of several thousand independent disorder realizations and using an observable that detects peaks in the overlap distribution, we show that the Sherrington-Kirkpatrick and Edwards-Anderson models have a distinctly different low-temperature behavior. The structure of the spin-glass overlap distribution for the Edwards-Anderson model suggests that its low-temperature phase has only a single pair of pure states. J. M. and B. Y. are supported in part by the NSF (Grant No. DMR-0907235 and DMR-1208046).

  19. Odd q-state clock spin-glass models in three dimensions, asymmetric phase diagrams, and multiple algebraically ordered phases.

    Science.gov (United States)

    Ilker, Efe; Berker, A Nihat

    2014-12-01

    Distinctive orderings and phase diagram structures are found, from renormalization-group theory, for odd q-state clock spin-glass models in d=3 dimensions. These models exhibit asymmetric phase diagrams, as is also the case for quantum Heisenberg spin-glass models. No finite-temperature spin-glass phase occurs. For all odd q≥5, algebraically ordered antiferromagnetic phases occur. One such phase is dominant and occurs for all q≥5. Other such phases occupy small low-temperature portions of the phase diagrams and occur for 5≤q≤15. All algebraically ordered phases have the same structure, determined by an attractive finite-temperature sink fixed point where a dominant and a subdominant pair states have the only nonzero Boltzmann weights. The phase transition critical exponents quickly saturate to the high q value.

  20. Comparison of silicone and spin-on glass packaging materials for light-emitting diode encapsulation

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Liann-Be; Pan, Ke-Wei; Yen, Chia-Yi [Department of Electronic Engineering and Green Technology Research Center, Chang Gung University, Taoyuan, Taiwan (China); Jeng, Ming-Jer, E-mail: mjjeng@mail.cgu.edu.tw [Department of Electronic Engineering and Green Technology Research Center, Chang Gung University, Taoyuan, Taiwan (China); Wu, Chun-Te; Hu, Sung-Cheng; Kuo, Yang-Kuao [Chemical Systems Research Division, Chung-Shan Institute of Science and Technology Armaments Bureau, MND, Taoyuan, Taiwan (China)

    2014-11-03

    Traditional white light light-emitting diode (LED) encapsulation is performed by mixed phosphors and silicone coating on LED die. However, this encapsulation with silicone coating incurs overheated temperatures and yellowing problem. Therefore, this work attempts to replace silicone paste by using spin-on-glass (SOG) materials. Experimental results indicate that although initial brightness of SOG-based packaging is lower than that of silicone packaging, its light attenuation is significantly lower than that of silicone for a long lighting time. After the LED power is turned on for 12 h, the brightness of LED with silicone and SOG material packaging decreases from 84 to 48 lm and 73 to 59 lm, respectively. Therefore, SOG material provides an alternative packaging solution for high power LED lighting applications. - Highlights: • Spin-on-glass (SOG) material was used to replace silicone coating for LED packaging. • Initial brightness of SOG packaging is lower than that of silicone packaging. • Over time, light attenuation in SOG is much lower than that in silicone. • Color rendering index and brightness of LED packaging was optimized by Taguchi method.

  1. Low-temperature spin-glass behavior in a diluted dipolar Ising system

    Science.gov (United States)

    Alonso, Juan J.

    2015-03-01

    Using Monte Carlo simulations, we study the character of the spin-glass (SG) state of a site-diluted dipolar Ising model. We consider systems of dipoles randomly placed on a fraction x of all L3 sites of a simple cubic lattice that point up or down along a given crystalline axis. For x ≲0.65 these systems are known to exhibit an equilibrium spin-glass phase below a temperature Tsg∝x . At high dilution and very low temperatures, well deep in the SG phase, we find spiky distributions of the overlap parameter q that are strongly sample dependent. We focus on spikes associated with large excitations. From cumulative distributions of q and a pair correlation function averaged over several thousands of samples we find that, for the system sizes studied, the average width of spikes, and the fraction of samples with spikes higher than a certain threshold, does not vary appreciably with L . This is compared with the behavior found for the Sherrington-Kirkpatrick model.

  2. Spin-cluster glass state in U(Ga0.95Mn0.05)3

    Science.gov (United States)

    Dong-Hua, Xie; Wen, Zhang; Yi, Liu; Wei, Feng; Yun, Zhang; Shi-Yong, Tan; Xie-Gang, Zhu; Qiu-Yun, Chen; Qin, Liu; Bing-Kai, Yuan; Xin-Chun, Lai

    2016-04-01

    We report the study of a low temperature cluster glass state in 5% Mn-doped UGa3 heavy fermion compound. This compound transforms from a paramagnetic state to a spin-cluster glass state, which is confirmed by measuring the dc susceptibility and magnetization. The ac susceptibility exhibits a frequency-dependent peak around T f, which provides direct evidence of the cluster glass state. By analyzing the field-dependent magnetization and frequency-dependent ac susceptibility in detail, we deduce that this compound forms a spin-cluster glass state below T f. Project supported by the Natural Science Foundation of China Academy of Engineering Physic (Grant No. 2014A0301013) and the National Natural Science Foundation of China (Grant Nos. 11304291 and 11504342).

  3. Phase Diagrams, Criticality, and Local Properties of Spin Glasses and Random-Field Ising Models from Renormalization - Calculations.

    Science.gov (United States)

    Hartford, Edward John

    This position-space renormalization-group study focuses on two systems with quenched disorder: the Ising spin glass and the asymmetric random-field Ising model. We have employed the Migdal-Kadanoff approach to determine local recursion relations and have retained the full correlated probability distribution of interactions and fields at each iteration in a series of histograms. We find an equilibrium spin-glass phase in three dimensions, but not in two. The spin glass is characterized by a distribution of effective interactions that broadens under iteration, signaling both the long-range order of the phase and the importance of competing interactions on all length scales. We have introduced a method to calculate the distribution of local properties by differentiating the free energy with respect to a particular magnetic field or interaction. Within the spin-glass phase, the nearest neighbor correlation ranges from negative one to one, showing the strong correlations and the local variation within the phase. The spin-glass-to-paramagnet phase transition is second order, with a smooth specific heat indicated by a negative critical exponent alpha. The multicritical point separating the spin-glass, paramagnetic, and ferromagnetic phases lies along the Nishimori line and also has a nondivergent specific heat. When the system undergoes quenched dilution, the resulting critical and multicritical behaviors are identical to those of the undiluted system. Even the addition of an infinitesimal magnetic field destroys the long-range spin-glass order; however, the characteristic broadening of the distribution continues for several iterations for small fields and low temperatures, suggesting the persistence of sizable spin-glass domains. Our study of the asymmetric random-field Ising model is motivated by recent experiments on phase transitions in porous media and mean-field treatments, which suggest that new critical behavior could occur when the distribution of fields is

  4. Quantum annealing search of Ising spin glass ground state(s) with tunable transverse and longitudinal fields

    Science.gov (United States)

    Rajak, A.; Chakrabarti, B. K.

    2014-09-01

    Here we first discuss briefly the quantum annealing technique. We then study the quantum annealing of Sherrington-Kirkpatrick spin glass model with the tuning of both transverse and longitudinal fields. Both the fields are time-dependent and vanish adiabatically at the same time, starting from high values. We solve, for rather small systems, the time-dependent Schrodinger equation of the total Hamiltonian by employing a numerical technique. At the end of annealing we obtain the final state having high overlap with the exact ground state(s) of classical spin glass system (obtained independently).

  5. A theoretical study of the spin glass-Kondo-magnetic disordered alloys in the presence of a random field

    Science.gov (United States)

    Magalhaes, S. G.; Zimmer, F. M.; Coqblin, B.

    2012-12-01

    We study here the influence of a random applied magnetic field on the competition between the Kondo effect, the spin glass phase and a ferromagnetic order in disordered cerium systems such as CeNi1-xCux. The model used here takes an intrasite Kondo coupling and an intersite random coupling; both the intersite random coupling and the random magnetic field are described within the Sherrington-Kirkpatrick model and the one-step replica symmetry breaking procedure is also used here. We present phase diagrams giving Temperature versus the Kondo exchange parameter and the random magnetic field makes decrease particularly the importance of the spin glass and ferromagnetic phases.

  6. Crystal structure of the new diamond-like semiconductor CuMn$_2$InSe$_4$

    Indian Academy of Sciences (India)

    G E DELGADO; V SAGREDO

    2016-12-01

    The crystal structure of the semiconductor compound CuMn$_2$InSe$_4$ was analysed using X-ray powder diffraction data. CuMn$_2$InSe$_4$ crystallizes, with a stannite structure, in the tetragonal space group I$\\bar{4}$2m (No. 121), $Z = 2$, with unit cell parameters $a = 5.8111(2) \\AA$, $c = 11.5739(8) \\AA$ and $V = 390.84(3) \\AA^#$. The refinement of 28 instrumental and structural parameters led to $R_{\\rm p} = 8.1$%, $R_{\\rm wp} = 10.5$%, $R_{\\rm exp} = 6.5$% and $S = 1.6,$ for 86 independent reflections.

  7. Metastable minima of the Heisenberg spin glass in a random magnetic field

    Science.gov (United States)

    Sharma, Auditya; Yeo, Joonhyun; Moore, M. A.

    2016-11-01

    We have studied zero-temperature metastable minima in classical m -vector component spin glasses in the presence of m -component random fields for two models, the Sherrington-Kirkpatrick (SK) model and the Viana-Bray (VB) model. For the SK model we have calculated analytically its complexity (the log of the number of minima) for both the annealed case where one averages the number of minima before taking the log and the quenched case where one averages the complexity itself, both for fields above and below the de Almeida-Thouless (AT) field, which is finite for m >2 . We have done numerical quenches starting from a random initial state (infinite temperature state) by putting spins parallel to their local fields until there is no further decrease of the energy and found that in zero field it always produces minima that have zero overlap with each other. For the m =2 and m =3 cases in the SK model the final energy reached in the quench is very close to the energy Ec at which the overlap of the states would acquire replica symmetry-breaking features. These minima have marginal stability and will have long-range correlations between them. In the SK limit we have analytically studied the density of states ρ (λ ) of the Hessian matrix in the annealed approximation. Despite the fact that in the presence of a random field there are no continuous symmetries, the spectrum extends down to zero with the usual √{λ } form for the density of states for fields below the AT field. However, when the random field is larger than the AT field, there is a gap in the spectrum, which closes up as the AT field is approached. The VB model behaves differently and seems rather similar to studies of the three-dimensional Heisenberg spin glass in a random vector field.

  8. Search for the Heisenberg spin glass on rewired square lattices with antiferromagnetic interaction

    Science.gov (United States)

    Surungan, Tasrief; Bansawang B., J.; Tahir, Dahlang

    2016-03-01

    Spin glass (SG) is a typical magnetic system with frozen random spin orientation at low temperatures. The system exhibits rich physical properties, such as infinite number of ground states, memory effect, and aging phenomena. There are two main ingredients considered to be pivotal for the existence of SG behavior, namely, frustration and randomness. For the canonical SG system, frustration is led by the presence of competing interaction between ferromagnetic (FM) and antiferromagnetic (AF) couplings. Previously, Bartolozzi et al. [Phys. Rev. B73, 224419 (2006)], reported the SG properties of the AF Ising spins on scale free network (SFN). It is a new type of SG, different from the canonical one which requires the presence of both FM and AF couplings. In this new system, frustration is purely caused by the topological factor and its randomness is related to the irregular connectvity. Recently, Surungan et. al. [Journal of Physics: Conference Series, 640, 012001 (2015)] reported SG bahavior of AF Heisenberg model on SFN. We further investigate this type of system by studying an AF Heisenberg model on rewired square lattices. We used Replica Exchange algorithm of Monte Carlo Method and calculated the SG order parameter to search for the existence of SG phase.

  9. NMR and NQR studies of quadrupolar effects in glasses and polycrystals with half-integer spins

    Science.gov (United States)

    Orengo-Aviles, Moises

    NMR and NQR techniques have been used in the present study to investigate glasses and polycrystalline compounds containing nuclei with half-integer spins such as: sp{11}B, sp{23}Na, sp{45}Sc, and sp{93}Nb. The low field ({˜}1.2{-}1.5 Tesla) continuous wave (CW) NMR experiments were performed using the Non-Adiabatic Superfast Passage (NASP) or the slow passage methods. A BRUKER MSL 300 pulsed NMR spectrometer was used for the high field (7.1 Tesla) studies. The CW NQR experiments at room and liquid nitrogen temperature were carried out on a home built Robinson-type spectrometer. Using pulsed NMR the sp{45}Sc response from the glass system CaO-Bsb2Osb3-Scsb2Osb3, yielded a first-order quadrupolar interaction with eta=0 and Qsb{cc}≈617 kHz. A new Sc site with Qsb{cc}=23.44 MHz and eta=0 was found in polycrystalline Scsb2Osb3 and it was confirmed by NQR. Employing the NASP method it was found that the fraction of four-coordinated (Nsb4) boron atoms in the alkali thioborate (Nasb2S-Bsb2Ssb3) glass system follows a 3x/(1 - x) relationship for x≤0.15, where x is the molar fraction of Nasb2S in the glass. For the NQR spectra the 10% Nasb2S content glass exhibited a broader NQR resonance than the NQR resonance for pure v-Bsb2Ssb3. The additional width was attributed to responses of BSsb3 units whose Qsb{cc} values differ somewhat from the BSsb3 units in the pure vitreous Bsb2Ssb3. The CW NASP method was used to study the sp{23}Na response in the Nasb2O*2SiOsb2 glass, heat treated in three ways: annealed, slow cooled and splat quenched. Subjecting the glass to rapid cooling will produce an increased range of values for the components of the electric field gradient (EFG), and, hence an increased range of values for Qsb{cc} and eta. This was observed for the slow cooled sample when compared with the annealed glass. The effect should be seen also from the slow cooled to the splat quenched sample, but this was not observed. Crystalline sodium disilicate was examined by both

  10. Critical behavior of mean-field spin glasses on a dilute random graph

    Energy Technology Data Exchange (ETDEWEB)

    De Sanctis, Luca [Dipartimento di Matematica e di Psicologia, Universita di Bologna, P.zza di Porta San Donato 5, 40126 Bologna (Italy); Barra, Adriano; Folli, Viola [Dipartimento di Fisica, Universita La Sapienza, P.le Aldo Moro 5, 00185 Roma (Italy)], E-mail: desanctis@dm.unibo.it, E-mail: adriano.barra@roma1.infn.it, E-mail: viola.folli@roma1.infn.it

    2008-05-30

    We provide a rigorous strategy to find the critical exponents of the overlaps for dilute spin glasses, in the absence of an external field. Such a strategy is based on the expansion of a suitably perturbed average of the overlaps, which is used in the formulation of the free energy as the difference between a cavity part and the derivative of the free energy itself, considered as a function of the connectivity of the model. We assume the validity of certain reasonable approximations, equivalent to assuming a second-order transition, e.g. that higher powers of overlap monomials are of smaller magnitude near the critical point, of which we do not provide a rigorous proof.

  11. Fluctuation-dissipation relation in a spin glass in the non-stationary regime

    Energy Technology Data Exchange (ETDEWEB)

    Herisson, D.; Ocio, M

    2003-05-01

    We present the first experimental determination of the time autocorrelation C(t',t) of magnetization in the non-stationary regime of a spin glass. Quantitative comparison with the corresponding response, the magnetic susceptibility {chi}(t',t), is made possible by the use of a new experimental setup allowing both measurements in the same conditions. Clearly, we observe a non-linear fluctuation-dissipation relation between C and {chi}, depending weakly on the waiting time t'. Following theoretical developments on mean-field models, and lately on short range ones, it is predicted that in the limit of long times, the {chi}(C) relationship should become independent on t'. A scaling procedure allows us to extrapolate to the limit of long waiting times.

  12. Conformal invariance and stochastic Loewner evolution processes in two-dimensional Ising spin glasses.

    Science.gov (United States)

    Amoruso, C; Hartmann, A K; Hastings, M B; Moore, M A

    2006-12-31

    We present numerical evidence that the techniques of conformal field theory might be applicable to two-dimensional Ising spin glasses with Gaussian bond distributions. It is shown that certain domain wall distributions in one geometry can be related to that in a second geometry by a conformal transformation. We also present direct evidence that the domain walls are stochastic Loewner (SLE) processes with kappa approximately 2.1. An argument is given that their fractal dimension d(f) is related to their interface energy exponent theta by d(f) - 1 = 3/[4(3 + theta)], which is consistent with the commonly quoted values d(f) approximately 1.27 and theta approximately -0.28.

  13. Zero-temperature quantum annealing bottlenecks in the spin-glass phase.

    Science.gov (United States)

    Knysh, Sergey

    2016-08-05

    A promising approach to solving hard binary optimization problems is quantum adiabatic annealing in a transverse magnetic field. An instantaneous ground state-initially a symmetric superposition of all possible assignments of N qubits-is closely tracked as it becomes more and more localized near the global minimum of the classical energy. Regions where the energy gap to excited states is small (for instance at the phase transition) are the algorithm's bottlenecks. Here I show how for large problems the complexity becomes dominated by O(log N) bottlenecks inside the spin-glass phase, where the gap scales as a stretched exponential. For smaller N, only the gap at the critical point is relevant, where it scales polynomially, as long as the phase transition is second order. This phenomenon is demonstrated rigorously for the two-pattern Gaussian Hopfield model. Qualitative comparison with the Sherrington-Kirkpatrick model leads to similar conclusions.

  14. Characterization of silanization and antibody immobilization on spin-on glass (SOG) surface

    Energy Technology Data Exchange (ETDEWEB)

    Nagare, Gajanan D. [School of Biosciences and Bio-Engineering, IIT Bombay (India); Mukherji, S. [School of Biosciences and Bio-Engineering, IIT Bombay (India)], E-mail: mukherji@iitb.ac.in

    2009-01-01

    Most embedded optical waveguide biosensors require low dielectric optical material. The prerequisites for such applications include the selection of an appropriate material and effective bio-functionalization. Spin-on glass (SOG) is one of the preferred polymers that can be easily deposited. Further, the chemical properties of the polymer make it amenable for bio-functionalization. This paper reports a detailed study of a protocol for immobilization of antibodies on SOG for possible immunobiosensor applications. The effect of silanization at different pH values on the number of free and usable amine sites was quantified by fluorimetry. Contact angle measurements, ellipsometry, AFM, and fluorescence microscopy was used for assessing the surface properties at various stages of preparation, functionalization and biomolecule immobilization.

  15. Extremal Optimization for Ground States of the Sherrington-Kirkpatrick Spin Glass with Levy Bonds

    Science.gov (United States)

    Boettcher, Stefan

    2013-03-01

    Using the Extremal Optimization heuristic (EO),[3] ground states of the SK-spin glass are studied with bonds J distributed according to a Levy distribution P (J) ~ 1 /| J | 1 + α with | J | > 1 and 1 model with Gaussian bonds.[4] We find that the energies attain universally the Parisi-energy of the SK when the second moment of P(J) exists (α > 2). They compare favorably with recent one-step replica symmetry breaking predictions well below α = 2 . Near α = 2 , the simulations deviate significantly from theoretical expectations. The finite-size corrections exponent ω decays from the putative SK value ωSK =2/3 already well above α = 2 . The exponent ρ for the scaling of ground state energy fluctuations with system size decays linearly from its SK value for decreasing α and vanishes at α = 1 . Supported through NSF grant DMR-#1207431

  16. Zero-temperature quantum annealing bottlenecks in the spin-glass phase

    Science.gov (United States)

    Knysh, Sergey

    2016-08-01

    A promising approach to solving hard binary optimization problems is quantum adiabatic annealing in a transverse magnetic field. An instantaneous ground state--initially a symmetric superposition of all possible assignments of N qubits--is closely tracked as it becomes more and more localized near the global minimum of the classical energy. Regions where the energy gap to excited states is small (for instance at the phase transition) are the algorithm's bottlenecks. Here I show how for large problems the complexity becomes dominated by O(log N) bottlenecks inside the spin-glass phase, where the gap scales as a stretched exponential. For smaller N, only the gap at the critical point is relevant, where it scales polynomially, as long as the phase transition is second order. This phenomenon is demonstrated rigorously for the two-pattern Gaussian Hopfield model. Qualitative comparison with the Sherrington-Kirkpatrick model leads to similar conclusions.

  17. SEMICONDUCTOR TECHNOLOGY Development of spin-on-glass process for triple metal interconnects

    Science.gov (United States)

    Li, Peng; Wenbin, Zhao; Guozhang, Wang; Zongguang, Yu

    2010-12-01

    Spin-on-glass (SOG), an interlayer dielectric material applied in liquid form to fill narrow gaps in the sub-dielectric surface and thus conducive to planarization, is an alternative to silicon dioxide (SiO2) deposited using PECVD processes. However, its inability to adhere to metal and problems such as cracking prevent the easy application of SOG technology to provide an interlayer dielectric in multilevel metal interconnect circuits, particularly in university processing labs. This paper will show that a thin layer of CVD SiO2 and a curing temperature below the sintering temperature of the metal interconnect layer will promote adhesion, reduce gaps, and prevent cracking. Electron scanning microscope analysis has been used to demonstrate the success of the improved technique. This optimized process has been used in batches of double-poly, triple-metal CMOS wafer fabrication to date.

  18. Study of dilution of Spin-On Glass by Fourier transform infrared spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Dominguez, Miguel, E-mail: mdominguez@inaoep.mx [National Institute for Astrophysics, Optics and Electronics (INAOE), Electronics Department, Luis Enrique Erro No. 1, Puebla 72840 (Mexico); Rosales, Pedro; Torres, Alfonso; Moreno, Mario [National Institute for Astrophysics, Optics and Electronics (INAOE), Electronics Department, Luis Enrique Erro No. 1, Puebla 72840 (Mexico); Orduna, Abdu [CIBA-Tlaxcala, Instituto Politecnico Nacional, Tepetitla, Tlax. 90700 (Mexico)

    2012-05-31

    In this work, we study the dilution of Spin-On Glass (SOG) in order to obtain high quality SiO{sub 2} films at 200 Degree-Sign C, with optical and electrical characteristics similar to those of the thermally grown SiO{sub 2}. For the production of SiO{sub 2} films we used 2-propanol and deionized water (DI) as diluents for the SOG and we compared the electrical and optical film properties with those of the films obtained from undiluted SOG. From Fourier transform infrared spectroscopy we observed a considerable reduction of Si-OH (920 cm{sup -1}), O-H (3490 cm{sup -1}) and C-H, C-O bonds (1139 cm{sup -1}) in the films produced from SOG diluted with DI. Besides the above, the insulator breakdown field was approximately 21 MV/cm, the refractive index and the dielectric constant were close to those of the thermally grown SiO{sub 2}. Our results suggest that the film produced from SOG diluted with DI and cured at 200 Degree-Sign C is an excellent candidate to be used as insulator on flexible and large-area electronics. - Highlights: Black-Right-Pointing-Pointer Preparation of high quality silicon oxide (SiO{sub 2}) films at 200 Degree-Sign C. Black-Right-Pointing-Pointer Dilution of Spin-On Glass (SOG) solution was studied. Black-Right-Pointing-Pointer Dilution of SOG is necessary to obtain high quality films annealed at 200 Degree-Sign C. Black-Right-Pointing-Pointer n and k are close to those of the thermally grown SiO{sub 2}.

  19. Scaling of the largest dynamical barrier in the one-dimensional long-range Ising spin glass

    Science.gov (United States)

    Monthus, Cécile; Garel, Thomas

    2014-01-01

    The long-range one-dimensional Ising spin glass with random couplings decaying as J(r )∝r-σ presents a spin-glass phase Tc(σ)>0 for 0≤σKirkpatrick model). We use the eigenvalue method introduced in our previous work (C. Monthus and T. Garel, J. Stat. Mech. 2009, P12017) to measure the equilibrium time teq(N ) at temperature T =Tc(σ)/2 as a function of the number N of spins. We find the activated scaling lnteq(N )¯˜Nψ with the same barrier exponent ψ ≃0.33 in the whole region 0≤σ<1.

  20. Existence of a Thermodynamic Spin-Glass Phase in the Zero-Concentration Limit of Anisotropic Dipolar Systems

    Science.gov (United States)

    Andresen, Juan Carlos; Katzgraber, Helmut G.; Oganesyan, Vadim; Schechter, Moshe

    2014-10-01

    The nature of ordering in dilute dipolar interacting systems dates back to the work of Debye and is one of the most basic, oldest and as-of-yet unsettled problems in magnetism. While spin-glass order is readily observed in several RKKY-interacting systems, dipolar spin glasses are the subject of controversy and ongoing scrutiny, e.g., in LiHoxY1 -xF4, a rare-earth randomly diluted uniaxial (Ising) dipolar system. In particular, it is unclear if the spin-glass phase in these paradigmatic materials persists in the limit of zero concentration or not. We study an effective model of LiHoxY1 -xF4 using large-scale Monte Carlo simulations that combine parallel tempering with a special cluster algorithm tailored to overcome the numerical difficulties that occur at extreme dilutions. We find a paramagnetic to spin-glass phase transition for all Ho+ ion concentrations down to the smallest concentration numerically accessible, 0.1%, and including Ho+ ion concentrations that coincide with those studied experimentally up to 16.7%. Our results suggest that randomly diluted dipolar Ising systems have a spin-glass phase in the limit of vanishing dipole concentration, with a critical temperature vanishing linearly with concentration. The agreement of our results with mean-field theory testifies to the irrelevance of fluctuations in interactions strengths, albeit being strong at small concentrations, to the nature of the low-temperature phase and the functional form of the critical temperature of dilute anisotropic dipolar systems. Deviations from linearity in experimental results at the lowest concentrations are discussed.

  1. Electron Spin Resonance and optical absorption spectroscopic studies of manganese centers in aluminium lead borate glasses

    Science.gov (United States)

    SivaRamaiah, G.; LakshmanaRao, J.

    2012-12-01

    Electron Spin Resonance (ESR) and optical absorption studies of 5Al2O3 + 75H3BO3 + (20-x)PbO + xMnSO4 (where x = 0.5, 1,1.5 and 2 mol% of MnSO4) glasses at room temperature have been studied. The ESR spectrum of all the glasses exhibits resonance signals with effective isotropic g values at ≈2.0, 3.3 and 4.3. The ESR resonance signal at isotropic g ≈ 2.0 has been attributed to Mn2+ centers in an octahedral symmetry. The ESR resonance signals at isotropic g ≈ 3.3 and 4.3 have been attributed to the rhombic symmetry of the Mn2+ ions. The zero-field splitting parameter (zfs) has been calculated from the intensities of the allowed hyperfine lines. The optical absorption spectrum exhibits an intense band in the visible region and it has been attributed to 5Eg → 5T2g transition of Mn3+centers in an octahedral environment. The optical band gap and the Urbach energies have been calculated from the ultraviolet absorption edges.

  2. Seeking Quantum Speedup Through Spin Glasses: The Good, the Bad, and the Ugly*

    Directory of Open Access Journals (Sweden)

    Helmut G. Katzgraber

    2015-09-01

    Full Text Available There has been considerable progress in the design and construction of quantum annealing devices. However, a conclusive detection of quantum speedup over traditional silicon-based machines remains elusive, despite multiple careful studies. In this work we outline strategies to design hard tunable benchmark instances based on insights from the study of spin glasses—the archetypal random benchmark problem for novel algorithms and optimization devices. We propose to complement head-to-head scaling studies that compare quantum annealing machines to state-of-the-art classical codes with an approach that compares the performance of different algorithms and/or computing architectures on different classes of computationally hard tunable spin-glass instances. The advantage of such an approach lies in having to compare only the performance hit felt by a given algorithm and/or architecture when the instance complexity is increased. Furthermore, we propose a methodology that might not directly translate into the detection of quantum speedup but might elucidate whether quantum annealing has a “quantum advantage” over corresponding classical algorithms, such as simulated annealing. Our results on a 496-qubit D-Wave Two quantum annealing device are compared to recently used state-of-the-art thermal simulated annealing codes.

  3. Real beards and real networks: a spin-glass model for interacting individuals

    Science.gov (United States)

    O'Neale, Dion

    ''I want to be different, just like all the other different people'' sang the band King Missile. Whether they are the Beatniks of the 1950s, the punks of the 1970s, or the hipsters of today, non-conformists often tend to look the same, seemingly at odds with their goal of non-conformity. The spin-glass model, originally developed to describe the interaction of magnetic spins, and since applied to situations as diverse as the electrical activity of networks of neurons, to trades on a financial market, has recently been used in social science to study populations of interacting individuals comprised of a mix of both conformists and anti-conformists - or hipsters. Including delay effects for the interactions between individuals has been shown to give a system with non-trivial dynamics with a phase transition from stable behaviour to periodic switching between two states (let's call them bushy bearded and clean shaven). Analytic solutions to such a model are possible, but only for particular assumptions about the interaction and delay matrices. In this work we will show what happens when the interactions in the model are based on real-world networks with ''small-world'' effects and clustering.

  4. Electron spin resonance and optical absorption spectroscopic studies of Cu{sup 2+} ions in aluminium lead borate glasses

    Energy Technology Data Exchange (ETDEWEB)

    SivaRamaiah, G., E-mail: gsivaram7@yahoo.co.in [Department of Physics, Government College for Men, Kadapa 516004 (India); LakshmanaRao, J., E-mail: jlrao46@yahoo.co.in [Department of Physics, Sri Venkateswara University, Tirupati 517502 (India)

    2013-02-25

    Highlights: Black-Right-Pointing-Pointer It is for the first time to study optical absorption and EPR in these glasses. Black-Right-Pointing-Pointer The thermal properties are new and interesting in this glass system. Black-Right-Pointing-Pointer It is for the first time to report three optical bands for Cu{sup 2+} in oxide glasses. Black-Right-Pointing-Pointer The interesting optical results are due to excellent sample preparation. - Abstract: Electron Spin Resonance and optical absorption spectral studies of Cu{sup 2+} ions in 5 Al{sub 2}O{sub 3} + 75 B{sub 2}O{sub 3} + (20-z) PbO + z CuO (where z = 0.1-1.5 mol.% of CuO) glasses have been reported. The EPR spectra of all the glasses show resonance signals characteristic of Cu{sup 2+} ions at both room and low temperatures. The number of spins and Gibbs energy were calculated at different concentrations and temperatures. From the plot of the ratio of logarithmic number of spins and absolute temperature and the reciprocal of absolute temperature, the entropy and enthalpy have been evaluated. The optical absorption spectra of all the glasses exhibit three bands and these bands have been assigned to {sup 2}B{sub 1g} {yields} {sup 2}E{sub g}, {sup 2}B{sub 1g} {yields} {sup 2}B{sub 2g}, and {sup 2}B{sub 1g} {yields} {sup 2}A{sub 1g} transitions in the decreasing order of energy. It is for the first time to observe three optical absorption bands for Cu{sup 2+} ions in oxide glasses. Such type of results is due to excellent sample preparation. From the EPR and optical absorption spectroscopies data, the molecular orbital coefficients have been evaluated.

  5. Boltzmann distribution of free energies in a finite-connectivity spin-glass system and the cavity approach

    Institute of Scientific and Technical Information of China (English)

    ZHOU Hai-jun

    2007-01-01

    At sufficiently low temperatures, the configurational phase space of a large spin-glass system breaks into many separated domains, each of which is referred to as a macroscopic state.The system is able to visit all spin configurations of the same macroscopic state, while it can not spontaneously jump between two different macroscopic states.Ergodicity of the whole configurational phase space of the system, however, can be recovered if a temperatureannealing process is repeated an infinite number of times.In a heating-annealing cycle, the environmental temperature is first elevated to a high level and then decreased extremely slowly until a final low temperature T is reached.Different macroscopic states may be reached in different rounds of the annealing experiment; while the probability of finding the system in macroscopic state a decreases exponentially with the free energy Fa(T) of this state.For finite-connectivity spin glass systems, we use this free energy Boltzmann disParisi [Eur.Phys.J.B, 2001, 20: 217] in a slightly different form.For the ±J spin-glass model on a random regular graph of degree K=6, the predictions of the present work agree with earlier simulational and theoretical results.

  6. Retrieving the ground state of spin glasses using thermal noise: Performance of quantum annealing at finite temperatures

    Science.gov (United States)

    Nishimura, Kohji; Nishimori, Hidetoshi; Ochoa, Andrew J.; Katzgraber, Helmut G.

    2016-09-01

    We study the problem to infer the ground state of a spin-glass Hamiltonian using data from another Hamiltonian with interactions disturbed by noise from the original Hamiltonian, motivated by the ground-state inference in quantum annealing on a noisy device. It is shown that the average Hamming distance between the inferred spin configuration and the true ground state is minimized when the temperature of the noisy system is kept at a finite value, and not at zero temperature. We present a spin-glass generalization of a well-established result that the ground state of a purely ferromagnetic Hamiltonian is best inferred at a finite temperature in the sense of smallest Hamming distance when the original ferromagnetic interactions are disturbed by noise. We use the numerical transfer-matrix method to establish the existence of an optimal finite temperature in one- and two-dimensional systems. Our numerical results are supported by mean-field calculations, which give an explicit expression of the optimal temperature to infer the spin-glass ground state as a function of variances of the distributions of the original interactions and the noise. The mean-field prediction is in qualitative agreement with numerical data. Implications on postprocessing of quantum annealing on a noisy device are discussed.

  7. Laser-induced radial birefringence and spin-to-orbital optical angular momentum conversion in silver-doped glasses

    CERN Document Server

    Amjad, Jafar Mostafavi; Slussarenko, Sergei; Karimi, Ebrahim; Marrucci, Lorenzo; Santamato, Enrico; 10.1063/1.3610474

    2012-01-01

    Samples of Ag$^+$/Na$^{+}$ ion-exchanged glass that have been subject to intense laser irradiation may develop novel optical properties, as a consequence of the formation of patterns of silver nanoparticles and other structures. Here, we report the observation of a laser-induced permanent transverse birefringence, with the optical axis forming a radial pattern, as revealed by the spin-to-orbital angular momentum conversion occurring in a probe light beam. The birefringence pattern can be modeled well as resulting from thermally-induced stresses arising in the silver-doped glass during laser exposure, although the actual mechanism leading to the permanent anisotropy is probably more complex.

  8. Laser-induced radial birefringence and spin-to-orbital optical angular momentum conversion in silver-doped glasses

    Science.gov (United States)

    Amjad, Jafar Mostafavi; Khalesifard, Hamid Reza; Slussarenko, Sergei; Karimi, Ebrahim; Marrucci, Lorenzo; Santamato, Enrico

    2011-07-01

    Samples of Ag+/Na+ ion-exchanged glass that have been subject to intense laser irradiation may develop novel optical properties, as a consequence of the formation of patterns of silver nanoparticles and other structures. Here, we report the observation of a laser-induced permanent transverse birefringence, with the optical axis forming a radial pattern, as revealed by the spin-to-orbital angular momentum conversion occurring in a probe light beam. The birefringence pattern can be modeled well as resulting from thermally-induced stresses arising in the silver-doped glass during laser exposure, although the actual mechanism leading to the permanent anisotropy is probably more complex.

  9. Fractal Dimension of Interfaces in Edwards-Anderson and Long-range Ising Spin Glasses: Determining the Applicability of Different Theoretical Descriptions

    Science.gov (United States)

    Wang, Wenlong; Moore, M. A.; Katzgraber, Helmut G.

    2017-09-01

    The fractal dimension of excitations in glassy systems gives information on the critical dimension at which the droplet picture of spin glasses changes to a description based on replica symmetry breaking where the interfaces are space filling. Here, the fractal dimension of domain-wall interfaces is studied using the strong-disorder renormalization group method pioneered by Monthus [Fractals 23, 1550042 (2015), 10.1142/S0218348X15500425] both for the Edwards-Anderson spin-glass model in up to 8 space dimensions, as well as for the one-dimensional long-ranged Ising spin-glass with power-law interactions. Analyzing the fractal dimension of domain walls, we find that replica symmetry is broken in high-enough space dimensions. Because our results for high-dimensional hypercubic lattices are limited by their small size, we have also studied the behavior of the one-dimensional long-range Ising spin-glass with power-law interactions. For the regime where the power of the decay of the spin-spin interactions with their separation distance corresponds to 6 and higher effective space dimensions, we find again the broken replica symmetry result of space filling excitations. This is not the case for smaller effective space dimensions. These results show that the dimensionality of the spin glass determines which theoretical description is appropriate. Our results will also be of relevance to the Gardner transition of structural glasses.

  10. Re-entrant spin-glass behaviour in CeAu{sub 2}Si{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Li, D.X. [Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan)], E-mail: dxli@imr.tohoku.ac.jp; Yamamura, T. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Nimori, S. [Tsukuba Magnet Laboratory, National Institute for Materials Science, 3-13 Sakura, Tsukuba 305-0003 (Japan); Shiokawa, Y. [Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan)

    2008-02-28

    We present the results of ac and dc susceptibility, magnetic relaxation, specific heat and electrical resistivity measurements on a well-annealed tetragonal ThCr{sub 2}Si{sub 2}-type compound CeAu{sub 2}Si{sub 2}. These data provide clear evidence for the formation of spin glass state in this system at about T{sub f} {approx} 2.2 K much lower than its Neel temperature T{sub N} = 10 K. The mechanism of the observed re-entrant spin-glass behaviour in CeAu{sub 2}Si{sub 2} is discussed by comparing the present results with those reported for the analogue compounds URh{sub 2}Ge{sub 2} and PrAu{sub 2}Si{sub 2}.

  11. Comparing Monte Carlo methods for finding ground states of Ising spin glasses: Population annealing, simulated annealing, and parallel tempering

    Science.gov (United States)

    Wang, Wenlong; Machta, Jonathan; Katzgraber, Helmut G.

    2015-07-01

    Population annealing is a Monte Carlo algorithm that marries features from simulated-annealing and parallel-tempering Monte Carlo. As such, it is ideal to overcome large energy barriers in the free-energy landscape while minimizing a Hamiltonian. Thus, population-annealing Monte Carlo can be used as a heuristic to solve combinatorial optimization problems. We illustrate the capabilities of population-annealing Monte Carlo by computing ground states of the three-dimensional Ising spin glass with Gaussian disorder, while comparing to simulated-annealing and parallel-tempering Monte Carlo. Our results suggest that population annealing Monte Carlo is significantly more efficient than simulated annealing but comparable to parallel-tempering Monte Carlo for finding spin-glass ground states.

  12. Antiferromagnetic versus spin-glass like behavior in MnIn{sub 2}S{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Sagredo, V. [Laboratorio de Magnetismo, Departamento de Fisica, Facultad de Ciencias, Universidad de los Andes, Merida (Venezuela)]. E-mail: sagredo@ula.ve; Moron, M.C. [Instituto de Ciencia de Materiales de Aragon, C.S.I.C.-Universidad de Zaragoza, E-50009, Zaragoza (Spain); Betancourt, L. [Laboratorio de Magnetismo, Departamento de Fisica, Facultad de Ciencias, Universidad de los Andes, Merida (Venezuela); Delgado, G.E. [Laboratorio de Cristalografia, Departamento de Quimica, Facultad de Ciencias, Universidad de los Andes, Merida (Venezuela)

    2007-05-15

    The low-temperature magnetic properties of MnIn{sub 2}S{sub 4} have been studied using AC magnetic susceptibility and magnetization experiments. High-temperature susceptibility fits indicate the presence of antiferromagnetic interactions. Low-field magnetization data show a peak at 5.6{+-}0.1 K, below which strong irreversibility is observed between zero-field-cooled (ZFC) and field-cooled (FC) cycles suggesting that the observed peak corresponds to a spin-glass-like transition instead of the antiferromagnetic one previously reported. Further evidence of this magnetic state comes from AC susceptibility data at different frequencies. The in-phase component {chi}'(T) exhibits the behavior expected of spin glasses, i.e. a shift of the cusp to higher temperatures for higher frequencies.

  13. Comparing Monte Carlo methods for finding ground states of Ising spin glasses: Population annealing, simulated annealing, and parallel tempering.

    Science.gov (United States)

    Wang, Wenlong; Machta, Jonathan; Katzgraber, Helmut G

    2015-07-01

    Population annealing is a Monte Carlo algorithm that marries features from simulated-annealing and parallel-tempering Monte Carlo. As such, it is ideal to overcome large energy barriers in the free-energy landscape while minimizing a Hamiltonian. Thus, population-annealing Monte Carlo can be used as a heuristic to solve combinatorial optimization problems. We illustrate the capabilities of population-annealing Monte Carlo by computing ground states of the three-dimensional Ising spin glass with Gaussian disorder, while comparing to simulated-annealing and parallel-tempering Monte Carlo. Our results suggest that population annealing Monte Carlo is significantly more efficient than simulated annealing but comparable to parallel-tempering Monte Carlo for finding spin-glass ground states.

  14. Short-range Ising spin glasses: The metastate interpretation of replica symmetry breaking

    Science.gov (United States)

    Read, N.

    2014-09-01

    Parisi's formal replica-symmetry-breaking (RSB) scheme for mean-field spin glasses has long been interpreted in terms of many pure states organized ultrametrically. However, the early version of this interpretation, as applied to the short-range Edwards-Anderson model, runs into problems because as shown by Newman and Stein (NS) it does not allow for chaotic size dependence, and predicts non-self-averaging that cannot occur. NS proposed the concept of the metastate (a probability distribution over infinite-size Gibbs states in a given sample that captures the effects of chaotic size dependence) and a nonstandard interpretation of the RSB results in which the metastate is nontrivial and is responsible for what was called non-self-averaging. In this picture, each state drawn from the metastate has the ultrametric properties of the old theory, but when the state is averaged using the metastate, the resulting mixed state has little structure. This picture was constructed so as to agree both with the earlier RSB results and with rigorous results. Here we use the effective field theory of RSB, in conjunction with the rigorous definitions of pure states and the metastate in infinite-size systems, to show that the nonstandard picture follows directly from the RSB mean-field theory. In addition, the metastate-averaged state possesses power-law correlations throughout the low-temperature phase; the corresponding exponent ζ takes the value 4 according to the field theory in high dimensions d, and describes the effective fractal dimension of clusters of spins. Further, the logarithm of the number of pure states in the decomposition of the metastate-averaged state that can be distinguished if only correlations in a window of size W can be observed is of order Wd -ζ. These results extend the nonstandard picture quantitatively; we show that arguments against this scenario are inconclusive. More generally, in terms of Parisi's function q (x), if q(0)≠∫01dxq(x ), then the

  15. Role of Fe magnetic subsystems to form a magnetic spin glass state in RFeTi2O7

    Science.gov (United States)

    Drokina, T. V.; Petrakovskii, G. A.; Bayukov, O. A.; Molokeev, M. S.; Bartolomé, J.; Arauzo, A.

    2017-10-01

    The experimental studies on R3+Fe3+Ti2O7 (R=Sm, Gd, Tb, Tm, Dy) magnetic properties evidence the low temperature spin glass state in all compounds. The possibility of rare-earth cation substitution allows the investigation of the role of magnetic iron Fe3+ ions and rare earth R3+ ions subsystems in a ground state formation in these oxide compounds.

  16. Evidence for two-dimensional spin-glass ordering in submonolayer Fe films on cleaved InAs surfaces.

    Science.gov (United States)

    Mochizuki, Toshimitsu; Masutomi, Ryuichi; Okamoto, Tohru

    2008-12-31

    Magnetotransport measurements have been performed on two-dimensional electron gases formed at InAs(110) surfaces covered with a submonolayer of Fe. Hysteresis in the magnetoresistance, a difference in remanent magnetoresistance between zero-field-cooling procedures and field-cooling procedures, and logarithmic time-dependent relaxation after magnetic field sweep are clearly observed at 1.7 K for a coverage of 0.42 monolayer. These features are associated with spin-glass ordering in the Fe film.

  17. Spin-glass phase transition and behavior of nonlinear susceptibility in the Sherrington-Kirkpatrick model with random fields

    Science.gov (United States)

    Morais, C. V.; Zimmer, F. M.; Lazo, M. J.; Magalhães, S. G.; Nobre, F. D.

    2016-06-01

    The behavior of the nonlinear susceptibility χ3 and its relation to the spin-glass transition temperature Tf in the presence of random fields are investigated. To accomplish this task, the Sherrington-Kirkpatrick model is studied through the replica formalism, within a one-step replica-symmetry-breaking procedure. In addition, the dependence of the Almeida-Thouless eigenvalue λAT (replicon) on the random fields is analyzed. Particularly, in the absence of random fields, the temperature Tf can be traced by a divergence in the spin-glass susceptibility χSG, which presents a term inversely proportional to the replicon λAT. As a result of a relation between χSG and χ3, the latter also presents a divergence at Tf, which comes as a direct consequence of λAT=0 at Tf. However, our results show that, in the presence of random fields, χ3 presents a rounded maximum at a temperature T* which does not coincide with the spin-glass transition temperature Tf (i.e., T*>Tf for a given applied random field). Thus, the maximum value of χ3 at T* reflects the effects of the random fields in the paramagnetic phase instead of the nontrivial ergodicity breaking associated with the spin-glass phase transition. It is also shown that χ3 still maintains a dependence on the replicon λAT, although in a more complicated way as compared with the case without random fields. These results are discussed in view of recent observations in the LiHoxY1 -xF4 compound.

  18. Luminescent Properties of Silicon Nanocrystals:Spin on Glass Hybrid Materials

    Directory of Open Access Journals (Sweden)

    Marco Antonio Vásquez-Agustín

    2017-01-01

    Full Text Available The photoluminescence characteristics of films consisting of Si nanocrystals either coated with or embedded into Spin on Glass (SOG were studied. Si nanocrystals showing red or blue luminescence when suspended in alcohol solution were obtained from porous silicon films. These were then either deposited in Si substrates and coated with SOG, or mixed in an SOG solution that was later spun on Si substrates. Both types of films were thermally annealed at 1100 °C for three hours in N2 atmosphere. Transmission electron microscopy measurements showed a mean diameter of 2.5 nm for the Si nanocrystals, as well as the presence of polycrystalline Si nanoagglomerates. These results were confirmed by X-ray diffraction studies, which revealed the (111, (220 and (311 Bragg peaks in Si nanocrystals. Fourier transform infrared spectroscopy studies showed that the coated films present higher chemical reactivity, promoting the formation of non-stoichiometric SiO2, while the embedded films behave as a stoichiometric SiO2 after the thermal annealing. The PL (photoluminescence characterization showed that both embedded and coated films present emission dominated by the Quantum Confinement Effect before undergoing any thermal treatment. After annealing, the spectra were found to be modified only in the case of the coated films, due to the formation of defects in the nanocrystals/SiO2 interface.

  19. Antiferromagnetic order and spin glass behavior in Dy{sub 2}CuIn{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Siouris, I.M., E-mail: jsiou@pme.duth.gr [Democritus University of Thrace (DUTH), Production and Management Engineering Department, Materials Laboratory, 67100 Xanthi (Greece); Kremer, R.K. [Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, D-70569 Stuttgart (Germany); Hoelzel, M. [Technische Universitaet Muenchen, Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), 85748 Garching (Germany)

    2011-11-15

    The magnetic properties of the intermetallic compound Dy{sub 2}CuIn{sub 3} have been investigated. Ac and dc-susceptibility measurements indicate an onset of antiferromagnetic ordering at T{sub N}=19.5 K and an additional frequency dependent transition at T{sub ds}{approx}9 K. Neutron diffraction studies confirm the ordered transition at 19.5{+-}1 K. The magnetic unit cell can be described by the propagation vector k=(0.25,0.25,0) with the magnetic moment {mu}=2.63(4){mu}{sub B}/Dy{sup 3+} parallel to the c-axis. Nevertheless, neutron diffraction reveals no additional magnetic phase transition around or below 9 K, which suggests that, at lower temperatures, a spin glass state may be formed in coexistence with the antiferromagnetic mode as a result of frustration and the antagonism between ferromagnetic and antiferromagnetic exchange interactions. - Highlights: > Dy{sub 2}CuIn{sub 3} is characterized by the dominance of antiferromagnetic (AF) interactions. > Geometric frustration and crystal field effects prevent the formation of the full magnetic moment on the Dy ions. > Two magnetic regimes are recognized: an AF state and a mixed AF-glassy state. > The antiferromagnetic structure of the compound has been determined.

  20. Spin glass behavior of the antiferromagnetic Heisenberg model on scale free network

    Science.gov (United States)

    Surungan, Tasrief; Zen, Freddy P.; Williams, Anthony G.

    2015-09-01

    Randomness and frustration are considered to be the key ingredients for the existence of spin glass (SG) phase. In a canonical system, these ingredients are realized by the random mixture of ferromagnetic (FM) and antiferromagnetic (AF) couplings. The study by Bartolozzi et al. [Phys. Rev. B73, 224419 (2006)] who observed the presence of SG phase on the AF Ising model on scale free network (SFN) is stimulating. It is a new type of SG system where randomness and frustration are not caused by the presence of FM and AF couplings. To further elaborate this type of system, here we study Heisenberg model on AF SFN and search for the SG phase. The canonical SG Heisenberg model is not observed in d-dimensional regular lattices for (d ≤ 3). We can make an analogy for the connectivity density (m) of SFN with the dimensionality of the regular lattice. It should be plausible to find the critical value of m for the existence of SG behaviour, analogous to the lower critical dimension (dl) for the canonical SG systems. Here we study system with m = 2, 3, 4 and 5. We used Replica Exchange algorithm of Monte Carlo Method and calculated the SG order parameter. We observed SG phase for each value of m and estimated its corersponding critical temperature.

  1. Stability conditions for fermionic Ising spin-glass models in the presence of a transverse field

    Science.gov (United States)

    Magalhães, S. G.; Zimmer, F. M.; Morais, C. V.

    2009-06-01

    The stability of a spin-glass (SG) phase is analyzed in detail for a fermionic Ising SG (FISG) model in the presence of a magnetic transverse field Γ. The fermionic path integral formalism, replica method and static approach have been used to obtain the thermodynamic potential within one step replica symmetry breaking ansatz. The replica symmetry (RS) results show that the SG phase is always unstable against the replicon. Moreover, the two other eigenvalues λ± of the Hessian matrix (related to the diagonal elements of the replica matrix) can indicate an additional instability to the SG phase, which enhances when Γ is increased. Therefore, this result suggests that the study of the replicon cannot be enough to guarantee the RS stability in the present quantum FISG model, especially near the quantum critical point. In particular, the FISG model allows changing the occupation number of sites, so one can get a first order transition when the chemical potential exceeds a certain value. In this region, the replicon and the λ± indicate instability problems for the SG solution close to all ranges of a first order boundary.

  2. A spin glass approach to the directed feedback vertex set problem

    CERN Document Server

    Zhou, Hai-Jun

    2016-01-01

    A directed graph (digraph) is formed by vertices and arcs (directed edges) from one vertex to another. A feedback vertex set (FVS) is a set of vertices that contains at least one vertex of every directed cycle in this digraph. The directed feedback vertex set problem aims at constructing a FVS of minimum cardinality. This is a fundamental cycle-constrained hard combinatorial optimization problem with wide practical applications. In this paper we construct a spin glass model for the directed FVS problem by converting the global cycle constraints into local arc constraints, and study this model through the replica-symmetric (RS) mean field theory of statistical physics. We then implement a belief propagation-guided decimation (BPD) algorithm for single digraph instances. The BPD algorithm slightly outperforms the simulated annealing algorithm on large random graph instances. The predictions of the RS mean field theory are noticeably lower than the BPD results, possibly due to its neglect of cycle-caused long ra...

  3. Low-temperature behavior of the statistics of the overlap distribution in Ising spin-glass models

    Science.gov (United States)

    Wittmann, Matthew; Yucesoy, B.; Katzgraber, Helmut G.; Machta, J.; Young, A. P.

    2014-10-01

    Using Monte Carlo simulations, we study in detail the overlap distribution for individual samples for several spin-glass models including the infinite-range Sherrington-Kirkpatrick model, short-range Edwards-Anderson models in three and four space dimensions, and one-dimensional long-range models with diluted power-law interactions. We study three long-range models with different powers as follows: The first is approximately equivalent to a short-range model in three dimensions, the second to a short-range model in four dimensions, and the third to a short-range model in the mean-field regime. We study an observable proposed earlier by some of us which aims to distinguish the "replica symmetry breaking" picture of the spin-glass phase from the "droplet picture," finding that larger system sizes would be needed to unambiguously determine which of these pictures describes the low-temperature state of spin glasses best, except for the Sherrington-Kirkpatrick model, which is unambiguously described by replica symmetry breaking. Finally, we also study the median integrated overlap probability distribution and a typical overlap distribution, finding that these observables are not particularly helpful in distinguishing the replica symmetry breaking and the droplet pictures.

  4. Spin-glass like behaviour in strongly interacting nanocrystalline Ni embedded in SiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    De, D. [Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India); Department of Physics, NITMAS, Diamond Harbour Road, 24 PGS (s), W.B. (India); Majumdar, S. [Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India); Giri, S., E-mail: sspsg2@iacs.res.in [Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India)

    2015-11-15

    Ni nanoparticles embedded in the SiO{sub 2} host are prepared by sol–gel route. Studies on X-ray diffraction and transmission electron microscopy confirm chemically single phase, good crystallinity and formation of nearly spherical nanoparticles with average size of 18 nm. Temperature dependence of zero field cooled (ZFC) magnetization shows a broad maximum around 230 K (T{sub max}), below which memory effect is observed in the field cooled (FC) and zero field cooled (ZFC) modes. A strong frequency dependence of ac susceptibility is observed around T{sub max} and the shift of peak position with frequency satisfies the dynamical scaling law with parameters close to that observed for atomic spin-glasses. At low temperature signature of spin-glass (SG) like behaviour is confirmed from the observed memory effect in the ZFC and isothermal remanent magnetization studies. The SG like behaviour is also apparent from the analysis of the relaxation mechanism. - Highlights: • Ni nanoparticles embedded in SiO{sub 2} host are prepared using sol–gel route. • Memory effect in ZFC and isothermal remanent magnetization are observed. • Static and dynamics of magnetization suggest spin-glass like behavior.

  5. Cu and Cu(Mn) films deposited layer-by-layer via surface-limited redox replacement and underpotential deposition

    Energy Technology Data Exchange (ETDEWEB)

    Fang, J.S., E-mail: jsfang@nfu.edu.tw [Department of Materials Science and Engineering, National Formosa University, Huwei 63201, Taiwan (China); Sun, S.L. [Department of Materials Science and Engineering, National Formosa University, Huwei 63201, Taiwan (China); Cheng, Y.L. [Department of Electrical Engineering, National Chi-Nan University, Nan-Tou 54561, Taiwan (China); Chen, G.S.; Chin, T.S. [Department of Materials Science and Engineering, Feng Chia University, Taichung 40724, Taiwan (China)

    2016-02-28

    Graphical abstract: - Abstract: The present paper reports Cu and Cu(Mn) films prepared layer-by-layer using an electrochemical atomic layer deposition (ECALD) method. The structure and properties of the films were investigated to elucidate their suitability as Cu interconnects for microelectronics. Previous studies have used primarily a vacuum-based atomic layer deposition to form a Cu metallized film. Herein, an entirely wet chemical process was used to fabricate a Cu film using the ECALD process by combining underpotential deposition (UPD) and surface-limited redox replacement (SLRR). The experimental results indicated that an inadequate UPD of Pb affected the subsequent SLRR of Cu and lead to the formation of PbSO{sub 4}. A mechanism is proposed to explain the results. Layer-by-layer deposition of Cu(Mn) films was successfully performed by alternating the deposition cycle-ratios of SLRR-Cu and UPD-Mn. The proposed self-limiting growth method offers a layer-by-layer wet chemistry-based deposition capability for fabricating Cu interconnects.

  6. Cu and Cu(Mn) films deposited layer-by-layer via surface-limited redox replacement and underpotential deposition

    Science.gov (United States)

    Fang, J. S.; Sun, S. L.; Cheng, Y. L.; Chen, G. S.; Chin, T. S.

    2016-02-01

    The present paper reports Cu and Cu(Mn) films prepared layer-by-layer using an electrochemical atomic layer deposition (ECALD) method. The structure and properties of the films were investigated to elucidate their suitability as Cu interconnects for microelectronics. Previous studies have used primarily a vacuum-based atomic layer deposition to form a Cu metallized film. Herein, an entirely wet chemical process was used to fabricate a Cu film using the ECALD process by combining underpotential deposition (UPD) and surface-limited redox replacement (SLRR). The experimental results indicated that an inadequate UPD of Pb affected the subsequent SLRR of Cu and lead to the formation of PbSO4. A mechanism is proposed to explain the results. Layer-by-layer deposition of Cu(Mn) films was successfully performed by alternating the deposition cycle-ratios of SLRR-Cu and UPD-Mn. The proposed self-limiting growth method offers a layer-by-layer wet chemistry-based deposition capability for fabricating Cu interconnects.

  7. Nature of the spin-glass phase in models with long-range interactions

    Science.gov (United States)

    Wittmann, Matthew C.

    Despite decades of effort, our understanding of low-temperature phase of spin glass models with short-range interactions remains incomplete. Replica symmetry breaking (RSB) theory, based on the solution of the Sherrington-Kirkpatrick mean-field model, predicts many pure states; meanwhile, competing theories of short-range systems, such as the droplet picture, predict a single pair of pure states related by time-reversal symmetry, analogously to the ferromagnet. Since RSB certainly holds for the mean-field (infinite-range) model, it is interesting to study short-range models in high dimensions to observe whether RSB also holds here; however, computer simulations of short-range models in high dimensions are difficult because the number of spins to equilibrate grows so rapidly with the linear size of the system. A relatively recent idea which has been fruitful is to instead study one-dimensional models with long-range (power-law) interactions, which are argued to have the same critical behavior as corresponding short-range models in high dimensions, but for which simulations for a range of sizes (crucial for finite-size scaling analysis) are feasible. For these one-dimensional long-range (1DLR) models, we fill in a previously unexplored region of parameter space where the interactions become sufficiently long-range that they must be rescaled with the system size to maintain the thermodynamic limit. We find strong evidence that detailed behavior of the 1DLR models everywhere in this "nonextensive regime" is identical to that of the Sherrington-Kirkpatrick model, lending support to a recent conjecture. In an attempt to distinguish the RSB and droplet pictures, we study recently-proposed observables based on the statistics of individual disorder samples, rather than simply averaging over the disorder as is most frequently done in previous studies. We compare Monte Carlo results for 1DLR models which are proxies for short-range models in 3, 4, and 10 dimensions with

  8. Glasses

    DEFF Research Database (Denmark)

    Dyre, Jeppe

    2004-01-01

    The temperature dependence of the viscosity of most glassforming liquids is known to depart significantly from the classical Arrhenius behaviour of simple fluids. The discovery of an unexpected correlation between the extent of this departure and the Poisson ratio of the resulting glass could lead...... to new understanding of glass ageing and viscous liquid dynamics....

  9. Glasses

    DEFF Research Database (Denmark)

    Dyre, Jeppe

    2004-01-01

    The temperature dependence of the viscosity of most glassforming liquids is known to depart significantly from the classical Arrhenius behaviour of simple fluids. The discovery of an unexpected correlation between the extent of this departure and the Poisson ratio of the resulting glass could lead...... to new understanding of glass ageing and viscous liquid dynamics....

  10. Spin-glass model predicts metastable brain states that diminish in anesthesia

    Directory of Open Access Journals (Sweden)

    Anthony G Hudetz

    2014-12-01

    Full Text Available Patterns of resting state connectivity change dynamically and may represent modes of cognitive information processing. The diversity of connectivity patterns (global brain states reflects the information capacity of the brain and determines the state of consciousness. In this work, computer simulation was used to explore the repertoire of global brain states as a function of cortical activation level. We implemented a modified spin glass model to describe UP/DOWN state transitions of neuronal populations at a mesoscopic scale based on resting state BOLD fMRI data. Resting state fMRI was recorded in 20 participants and mapped to 10,000 cortical regions defined on a group-aligned cortical surface map. Each region represented the population activity of a ~20mm2 area of the cortex. Cross-correlation matrices of the mapped BOLD time courses of the set of regions were calculated and averaged across subjects. In the model, each cortical region was allowed to interact with the 16 other regions that had the highest pair-wise correlation values. All regions stochastically transitioned between UP and DOWN states under the net influence of their 16 pairs. The probability of local state transitions was controlled by a single parameter T corresponding to the level of global cortical activation. To estimate the number of distinct global states, first we ran 10,000 simulations at T=0. Simulations were started from random configurations that converged to one of several distinct patterns. Using hierarchical clustering, at 99% similarity, close to 300 distinct states were found. At intermediate T, metastable state configurations were formed suggesting critical behavior with a sharp increase in the number of metastable states at an optimal T. Both reduced activation (anesthesia, sleep and increased activation (hyper-activation moved the system away from equilibrium, presumably incompatible with conscious mentation. During equilibrium, the diversity of large

  11. Spin-glass model predicts metastable brain states that diminish in anesthesia.

    Science.gov (United States)

    Hudetz, Anthony G; Humphries, Colin J; Binder, Jeffrey R

    2014-01-01

    Patterns of resting state connectivity change dynamically and may represent modes of cognitive information processing. The diversity of connectivity patterns (global brain states) reflects the information capacity of the brain and determines the state of consciousness. In this work, computer simulation was used to explore the repertoire of global brain states as a function of cortical activation level. We implemented a modified spin glass model to describe UP/DOWN state transitions of neuronal populations at a mesoscopic scale based on resting state BOLD fMRI data. Resting state fMRI was recorded in 20 participants and mapped to 10,000 cortical regions (sites) defined on a group-aligned cortical surface map. Each site represented the population activity of a ~20 mm(2) area of the cortex. Cross-correlation matrices of the mapped BOLD time courses of the set of sites were calculated and averaged across subjects. In the model, each cortical site was allowed to interact with the 16 other sites that had the highest pair-wise correlation values. All sites stochastically transitioned between UP and DOWN states under the net influence of their 16 pairs. The probability of local state transitions was controlled by a single parameter T corresponding to the level of global cortical activation. To estimate the number of distinct global states, first we ran 10,000 simulations at T = 0. Simulations were started from random configurations that converged to one of several distinct patterns. Using hierarchical clustering, at 99% similarity, close to 300 distinct states were found. At intermediate T, metastable state configurations were formed suggesting critical behavior with a sharp increase in the number of metastable states at an optimal T. Both reduced activation (anesthesia, sleep) and increased activation (hyper-activation) moved the system away from equilibrium, presumably incompatible with conscious mentation. During equilibrium, the diversity of large-scale brain states

  12. Response to a field of the D = 3 Ising spin glass with Janus and JanusII dedicated computers

    Science.gov (United States)

    Seoane, Beatriz; Janus Collaboration Collaboration

    Using the Janus dedicated computer, and its new generation JanusII, we study the linear response to a field of the Edwards-Anderson model for times that cover twelve orders of magnitude. The fluctuation-dissipation relations are investigated for several values of tw. We observe that the violations of the fluctuation-dissipation theorem can be directly related to the P (q) measured in equilibrium at finite sizes, although a simple statics-dynamics dictionary L ξ (tw) is not enough to account for the behavior at large times. We show that the equivalence can be easily restored by taking into account the growth of ξ (t +tw) . Interestingly, experimental measurements of the spin glass correlation length rely precisely on the response of a spin glass to a field, although a direct relation between the measured object and the real ξ has never been established. In this work, we mimic the experimental protocol with Janus data, which lets us relate the experimental ξ with the length extracted from the spatial correlation function. These results allow us for the first time to make a quantitative comparison between experiments and simulations, finding a surprising good agreement with measurements in superspin glasses. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 654971, the ERC grant CRIPHERASY (no. 247328) and from the MINECO(Spain) (No. FIS2012-35719-C02).

  13. Spin-glass behaviors in carrier polarity controlled Fe{sub 3−x}Ti{sub x}O{sub 4} semiconductor thin films

    Energy Technology Data Exchange (ETDEWEB)

    Yamahara, H., E-mail: yamahara@bioxide.t.u-tokyo.ac.jp [Institute of Engineering Innovation, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Seki, M.; Adachi, M.; Takahashi, M.; Nasu, H.; Tabata, H. [Department of Electrical Engineering and Information Systems, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Horiba, K.; Kumigashira, H. [KEK, Photon Factory, Tsukuba, Ibaraki 305-0801 (Japan)

    2015-08-14

    Carrier-type control of spin-glass (cluster spin-glass) is studied in order to engineer basic magnetic semiconductor elements using the memory functions of spin-glass. A key of carrier-polarity control in magnetite is the valence engineering between Fe(II) and Fe(III) that is achieved by Ti(IV) substitution. Single phases of (001)-oriented Fe{sub 3−x}Ti{sub x}O{sub 4} thin films have been obtained on spinel MgAl{sub 2}O{sub 4} substrates by pulsed laser deposition. Thermoelectric power measurements reveal that Ti-rich films (x = 0.8) show p-type conduction, while Ti-poor films (x = 0.6–0.75) show n-type conduction. The systematic Fe(III) reduction to Fe(II) followed by Ti(IV) substitution in the octahedral sublattice is confirmed by the X-ray absorption spectra. All of the Fe{sub 3−x}Ti{sub x}O{sub 4} films (x = 0.6–0.8) exhibit ferrimagnetism above room temperature. Next, the spin-glass behaviors of Ti-rich Fe{sub 2.2}Ti{sub 0.8}O{sub 4} film are studied, since this magnetically diluted system is expected to exhibit the spin-glass behaviors. The DC magnetization and AC susceptibility measurements for the Ti-rich Fe{sub 2.2}Ti{sub 0.8}O{sub 4} film reveal the presence of the spin glass phase. Thermal- and magnetic-field-history memory effects are observed and are attributed to the long time-decay nature of remanent magnetization. The detailed analysis of the time-dependent thermoremanent magnetization reveals the presence of the cluster spin glass state.

  14. Nicholas Metropolis Award for Outstanding Doctoral Thesis Work in Computational Physics Lecture: The Janus computer, a new window into spin-glass physics

    Science.gov (United States)

    Yllanes, David

    2013-03-01

    Spin glasses are a longstanding model for the sluggish dynamics that appears at the glass transition. They enjoy a privileged status in this context, as they provide the simplest model system both for theoretical and experimental studies of glassy dynamics. However, in spite of forty years of intensive investigation, spin glasses still pose a formidable challenge to theoretical, computational and experimental physics. The main difficulty lies in their incredibly slow dynamics. A recent breakthrough has been made possible by our custom-built computer, Janus, designed and built in a collaboration formed by five universities in Spain and Italy. By employing a purpose-driven architecture, capable of fully exploiting the parallelization possibilities intrinsic to these simulations, Janus outperforms conventional computers by several orders of magnitude. After a brief introduction to spin glasses, the talk will focus on the new physics unearthed by Janus. In particular, we recall our numerical study of the nonequilibrium dynamics of the Edwards-Anderson Ising Spin Glass, for a time that spans eleven orders of magnitude, thus approaching the experimentally relevant scale (i.e. seconds). We have also studied the equilibrium properties of the spin-glass phase, with an emphasis on the quantitative matching between non-equilibrium and equilibrium correlation functions, through a time-length dictionary. Last but not least, we have clarified the existence of a glass transition in the presence of a magnetic field for a finite-range spin glass (the so-called de Almeida-Thouless line). We will finally mention some of the currently ongoing work of the collaboration, such as the characterization of the non-equilibrium dynamics in a magnetic field and the existence of a statics-dynamics dictionary in these conditions.

  15. A Note on the Guerra and Talagrand Theorems for Mean Field Spin Glasses: The Simple Case of Spherical Models

    Science.gov (United States)

    Franz, Silvio; Tria, Francesca

    2006-01-01

    The aim of this paper is to discuss the main ideas of the Talagrand proof of the Parisi Ansatz for the free-energy of Mean Field Spin Glasses with a physicist's approach. We consider the case of the spherical p-spin model, which has the following advantages: (1) the Parisi Ansatz takes the simple "one step replica symmetry breaking form," (2) the replica free-energy as a function of the order parameters is simple enough to allow for numerical maximization with arbitrary precision. We present the essential ideas of the proof, we stress its connections with the theory of effective potentials for glassy systems, and we reduce the technically more difficult part of the Talagrand's analysis to an explicit evaluation of the solution of a variational problem.

  16. Mechanisms and application of the Excimer laser doping from spin-on glass sources for USJ fabrication

    Energy Technology Data Exchange (ETDEWEB)

    Coutanson, S. [InESS, 23 rue du Loess BP20 CR, F-67037 Strasbourg Cedex 2 (France); Fogarassy, E. [InESS, 23 rue du Loess BP20 CR, F-67037 Strasbourg Cedex 2 (France); Venturini, J. [SOPRA-SA, 26 rue Pierre Joigneaux, 92270 Bois-Colombes (France)

    2006-04-30

    In this work was investigated numerically and experimentally a simple laser doping method employing borosilicate (BSG) glass films as dopant sources which are deposited onto Si by the spin-coating technique. Both short (20 ns) and long (200 ns) pulse duration Excimer laser beams were used to deposit a large amount of energy in short time onto the near-surface region. Under suitable conditions, the irradiation leads to surface melting and dopant incorporation by liquid phase diffusion from the surface. Boron distribution profiles in the two-pulse duration regimes were studied as well as their electrical properties, and the junction formation of less than 25 nm in depth was demonstrated.

  17. Interface free-energy exponent in the one-dimensional Ising spin glass with long-range interactions in both the droplet and broken replica symmetry regions

    Science.gov (United States)

    Aspelmeier, T.; Wang, Wenlong; Moore, M. A.; Katzgraber, Helmut G.

    2016-08-01

    The one-dimensional Ising spin-glass model with power-law long-range interactions is a useful proxy model for studying spin glasses in higher space dimensions and for finding the dimension at which the spin-glass state changes from having broken replica symmetry to that of droplet behavior. To this end we have calculated the exponent that describes the difference in free energy between periodic and antiperiodic boundary conditions. Numerical work is done to support some of the assumptions made in the calculations and to determine the behavior of the interface free-energy exponent of the power law of the interactions. Our numerical results for the interface free-energy exponent are badly affected by finite-size problems.

  18. Reentrant spin glass behavior in polycrystalline La0.7Sr0.3Mn1-XFeXO 3

    Directory of Open Access Journals (Sweden)

    Xavier Jr. M.M.

    2004-01-01

    Full Text Available The magnetic and transport properties of the compound La0.7Sr0.3Mn1-xFe xO 3 (0.1 < x <0.4 have been studied by means of electrical resistivity, AC magnetic susceptibility, and DC magnetization. At low concentrations (x <0.1, the system displays essentially para-to-ferromagnetic transitions as the temperature is decreased, although a decrease in the magnetic moment has been observed in previous studies at temperatures a little below T C. This ferromagnetism is explained by double exchange theory in terms of the formation of Mn+3/Mn+4 ions pairs in the system. At concentrations in the range 0.1 < x <0.4 the system is more complex. Increased Fe doping not only weakens the ferromagnetic (FM order and augments the resistivity of the samples, but also induces the appearance of a reentrant spin glass phase at low temperatures (T < 60 K. Irreversibility of the magnetization measured with zero field cooling and with field cooling has been observed. In addition, the AC susceptibility peak position varies with frequency. All these effects are characteristic of spin glass behavior. The results have been interpreted based in an increase of frustration due to increasing competition between FM Mn+3/Mn+4 interactions and antiferromagnetic interactions between ions at the boundaries of Fe clusters.

  19. Study on the spin crossover transition and glass transition for Fe(II) complex film, [Fe(II)(H-triazole){sub 3}]-Nafion, by means of Moessbauer spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Nakamoto, Akio; Kamebuchi, Hajime, E-mail: cc106909@mail.ecc.u-tokyo.ac.jp [University of Tokyo, Graduate School of Arts and Sciences (Japan); Enomoto, Masaya [Tokyo University of Science, Department of Chemistry, Faculty of Science Division I (Japan); Kojima, Norimichi [University of Tokyo, Graduate School of Arts and Sciences (Japan)

    2012-03-15

    [Fe(II)(H-trz){sub 3}]-Nafion (trz = triazole) is a transparent spin crossover complex film, where the spin crossover transition between the low-spin (S = 0) and the high-spin (S = 2) states takes place between 225 K and 300 K. In this film, two doublets corresponding to the low-spin and high-spin states were observed in the {sup 57}Fe Moessbauer spectra, reflecting the spin crossover transition. From the analysis of {sup 57}Fe Moessbauer spectra, the Debye temperatures of the low-spin and high-spin sites were estimated at 185 K and 176 K, respectively, in the temperature range between 10 K and 150 K. In this film, the total intensity of the Moessbauer spectra corresponding to the low-spin and high-spin sites drastically decreases above 200 K, reflecting the glass transition of Nafion, where the lattice vibration of [Fe(H-trz){sub 3}]{sub n}{sup 2n+} is softened just as in solution due to micro-Brown motion of the segment of Nafion polymer membrane.

  20. Ground-state energy and entropy of the two-dimensional Edwards-Anderson spin-glass model with different bond distributions

    Science.gov (United States)

    Perez-Morelo, D. J.; Ramirez-Pastor, A. J.; Romá, F.

    2012-02-01

    We study the two-dimensional Edwards-Anderson spin-glass model using a parallel tempering Monte Carlo algorithm. The ground-state energy and entropy are calculated for different bond distributions. In particular, the entropy is obtained by using a thermodynamic integration technique and an appropriate reference state, which is determined with the method of high-temperature expansion. This strategy provides accurate values of this quantity for finite-size lattices. By extrapolating to the thermodynamic limit, the ground-state energy and entropy of the different versions of the spin-glass model are determined.

  1. [Study on the orientation of liquid crystals presented on the glass substrates spin-coated and functionalized with copper ions].

    Science.gov (United States)

    Wang, Shiming; Xiong, Xingliang; Zhang, Yan; Li, Guang; Chen, Mengmeng

    2013-06-01

    A stable, uniform, easily implemented, LC-based chemical and biological sensor substrate for orientations of liquid crystals (LCs) for a long-term is urgently needed for medical applications of the sensors. We proposed a use of spin-coating of copper perchlorate (Cu(ClO4)2), with five different concentrations(0-100mmol/L), directly on glass slides for fabricating a layer of chemically-sensitive copper ions. Observing the transmitted light with a polarized microscope, we found the luminosity of the light propagated through sensors deposited with copper ions started to weaken gradually after a certain time. The higher was the concentration of copper ions covered on the glass substrates of the sensors, the faster the weakening occurred, and the less time was needed for transmitted light to turn completely dark. But there was no change in luminosity of the transmitted light for the sensors without Cu(ClO4)2 spin-coating even after stored at room temperature (25 degrees C) for a whole day. When the Cu(ClO4)2 deposited sensors were stored within a drying oven at room temperature (25 degrees C) for 2 months, it was found that there vas almost no change in luminosity of the transmitted lights. The results showed that all the thin films of LC on glass slides functionalized with Cu(ClO4)2 could keep homeotropic and stable orientation for a long time; the concentration of Cu (ClO4)2I has an influence on the orientation response speed of LC from planar to perpendicular orientation.

  2. Spin-glass behavior of warwickite MgFeBO{sub 4} and CoFeBO{sub 4} crystals observed by Mössbauer spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lyubutin, I.S.; Korotkov, N. Yu.; Frolov, K.V. [Shubnikov Institute of Crystallography, RAS, 119333 Moscow (Russian Federation); Kazak, N.V.; Platunov, M.S. [Kirensky Institute of Physics, SB of RAS, 660036 Krasnoyarsk (Russian Federation); Knyazev, Yu. V. [Siberian Federal University, 660074 Krasnoyarsk (Russian Federation); Bezmaternykh, L.N. [Kirensky Institute of Physics, SB of RAS, 660036 Krasnoyarsk (Russian Federation); Ovchinnikov, S.G. [Kirensky Institute of Physics, SB of RAS, 660036 Krasnoyarsk (Russian Federation); Siberian Federal University, 660074 Krasnoyarsk (Russian Federation); Siberian State Aerospace University, 660014 Krasnoyarsk (Russian Federation); Arauzo, A. [Servicio de Medidas Físicas, Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza (Spain); Bartolomé, J. [Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza and Departamento de Física de la Materia Condensada, 50009 Zaragoza (Spain)

    2015-09-05

    Highlights: • Spin-glass behavior of MgFeBO{sub 4} and CoFeBO{sub 4} observed by Mössbauer spectroscopy. • Transition temperature T{sub SG} increases strongly with Co substitution. • Dynamical scaling theory near T{sub SG} is fulfilled. • Spin-glass behavior is explained as due to short range correlations. • Inclusion of Co increases exchange interaction and magnetocrystalline anisotropy. - Abstract: Single crystals of MgFeBO{sub 4} and CoFeBO{sub 4} warwickites were obtained. The effects of charge ordering and magnetic properties were investigated by Mössbauer spectroscopy. Cation distribution over M1 and M2 nonequivalent sites and the average charge at the metal positions were established. Low temperature Mössbauer spectra reveal spin-glass behavior, with spin-freezing temperatures T{sub SG} of 15.2 and 33.2 K for Mg- and Co-warwickites, respectively, higher than that observed from the d.c. and a.c. magnetic susceptibility measurements. The difference is explained in terms of dynamical scaling theory. The specific shape of the Mössbauer spectra in the vicinity of the magnetic transition at T{sub SG} shows the difference between spin-glass and superparamagnetic behavior and demonstrates an overwhelming role of the exchange anisotropy in the properties of Mg-warwickite. In Co-warwickite the increase of magnetocrystalline anisotropy provokes an increase in magnetic viscosity.

  3. Long-range quantum Ising spin glasses at t=0: gapless collective excitations and universality.

    Science.gov (United States)

    Andreanov, A; Müller, M

    2012-10-26

    We solve the Sherrington-Kirkpatrick model in a transverse field Γ deep in its quantum glass phase at zero temperature. We show that the glass phase is critical everywhere, exhibiting collective excitations with a gapless Ohmic spectral function. Using an effective potential approach, we interpret the latter as arising from disordered collective excitations behaving like weakly coupled, underdamped oscillators. For a small transverse field Γ, the low-frequency spectrum takes a form independent of the fluctuation strength Γ.

  4. Long-Range Quantum Ising Spin Glasses at T=0: Gapless Collective Excitations and Universality

    Science.gov (United States)

    Andreanov, A.; Müller, M.

    2012-10-01

    We solve the Sherrington-Kirkpatrick model in a transverse field Γ deep in its quantum glass phase at zero temperature. We show that the glass phase is critical everywhere, exhibiting collective excitations with a gapless Ohmic spectral function. Using an effective potential approach, we interpret the latter as arising from disordered collective excitations behaving like weakly coupled, underdamped oscillators. For a small transverse field Γ, the low-frequency spectrum takes a form independent of the fluctuation strength Γ.

  5. Chirality-driven intrinsic spin-glass ordering and field-induced ferromagnetism in Ni3Al nanoparticle aggregates

    Science.gov (United States)

    Kaul, S. N.; Messala, Umasankar

    2016-03-01

    Weak itinerant-electron ferromagnet Ni3Al is driven to magnetic instability (quantum critical point, QCP, where the long-range ferromagnetic order of the bulk ceases to exist) by reducing the average crystallite size to d=50 nm. 'Zero-field' (H=0) linear and nonlinear ac-susceptibilities, measured on Ni3Al nanoparticle aggregates, with d=50 nm (S1) and d=5 nm (S2), provide strong evidence for two spin glass (SG)-like thermodynamic phase transitions: one at Ti(H = 0) ≃ 30 K (Ti† (H = 0) ≃ 230 K) and the other at a lower temperature Tp(H = 0) ≃ 8 K (Th(H = 0) ≃ 52 K) in S1 (S2). 'In-field' (H ≠ 0) linear ac-susceptibility and dc magnetization demonstrate that the thermodynamic nature of these transitions is preserved in finite fields. The presently determined H-T phase diagrams for the samples S1 and S2 are compared with those predicted by the Kotliar-Sompolinsky and Gabay-Toulouse mean-field models and Monte Carlo simulations, based on the chirality-driven spin glass (SG) ordering scenario, for a three-dimensional nearest-neighbor Heisenberg SG system with or without weak random anisotropy. Such a detailed comparison permits us to unambiguously identify various 'zero-field' and 'in-field' SG phase transitions as: (i) the simultaneous paramagnetic (PM)-chiral glass (CG) and PM-SG phase transitions at Ti(H), (ii) the PM-CG transition at Ti† (H), (iii) the replica symmetry-breaking SG transition at Tp(H), and (iv) the continuous spin-rotation symmetry-breaking SG transition at Th(H). In the presence of random anisotropy, magnetization fails to saturate even at 90 kOe in S1 whereas negligibly small anisotropy allows even fields as weak as 1 kOe to saturate magnetization and induce ferromagnetism in S2. Due to the proximity to CG/SG-QCP, magnetization and susceptibility both exhibit non-Fermi liquid behavior over a wide range at low temperatures.

  6. Spin-glass-like behaviour in ball milled Fe{sub 30}Cr{sub 70} alloy studied by ac magnetic susceptibility

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Blanco, D.; Gorria, P. [Departamento de Fisica, Universidad de Oviedo, Calvo Sotelo, s/n, 33007 Oviedo (Spain); Fernandez-Martinez, Alejandro [Lawrence Livermore National Laboratory 7000 East Avenue, Livermore, CA 9455 (United States); Perez, M.J. [Departamento de Fisica, Universidad de Oviedo, Calvo Sotelo, s/n, 33007 Oviedo (Spain); Cuello, Gabriel J. [Institut Laue-Langevin, BP 156, 6, rue Jules Horowitz, 38042 Grenoble Cedex 9 (France); Blanco, J.A., E-mail: jabr@uniovi.es [Departamento de Fisica, Universidad de Oviedo, Calvo Sotelo, s/n, 33007 Oviedo (Spain)

    2011-06-15

    Research highlights: > Spin-glass-like behaviour o owing an re-entrant spin-glass transition. > No critical divergence observed in the maxima of the real and magnetic susceptibility on ball milled Fe{sub 30}Cr{sub 70}. > High temperature Curie-Weiss behavior of the magnetic susceptibility on ball milled Fe{sub 30}Cr{sub 70}. > Moderate shift of the freezing temperature per frequency in ball milled Fe{sub 30}Cr{sub 70} obtained from the temperature dependence of the real magnetic susceptibility - Abstract: Nominal nanostructured Fe{sub 30}Cr{sub 70} obtained from ball milling during 110 h has been investigated from dc magnetization and ac magnetic susceptibility. The as-milled sample is not monophasic and is formed of two phases, Fe{sub 20{+-}2}Cr{sub 80{+-}2} ({approx}86 {+-} 2%) and iron ({approx}14 {+-} 2%). The ac susceptibility measurements show evidence of a re-entrant spin-glass-like transition for the Fe{sub 20}Cr{sub 80} phase below 30 K. The shift of the freezing temperature per frequency decade is moderate when compared to that found in conventional spin-glass alloys. A Vogel-Fulcher activation process can be used to explain the frequency variation. The results are also analyzed in terms of Cole-Cole formalism for extracting information of relaxation time ({tau} {approx} 10{sup -5} to 10{sup -4} s).

  7. Static magnetic properties and relaxation of the insulating spin glass Co1-xMnxCl2.H2O

    Science.gov (United States)

    Defotis, G. C.; Coker, G. S.; Jones, J. W.; Branch, C. S.; King, H. A.; Bergman, J. S.; Lee, S.; Goodey, J. R.

    1998-11-01

    The magnetic properties of Co1-xMnxCl2.H2O are examined by dc magnetization and susceptibility measurements, for x=0.05, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, and 0.95 between 1.8 and 300 K. The pure components are a quasi-one-dimensional Heisenberg antiferromagnet (Mn) and an antiferromagnetic reentrant spin glass (Co) with some low-dimensional character. The Curie and Weiss constants, in χM=C/(T-θ), show regular composition dependence, with θ(x) varying nonlinearly from positive to negative values as x increases. Antiferromagnetic maxima often occur, and transition temperatures are estimated for most mixtures. The T-x diagram shows two descending boundaries from either composition extreme; any transition temperatures for x=0.5-0.8 are lower than we can measure. Magnetization isotherms evolve with composition, and associated hysteretic effects weaken with increasing x. The nonlinear susceptibility for x=0.30 shows structure, but does not diverge. The thermoremanent magnetization (TRM) is examined in detail for x=0.30, 0.40, and 0.50. Its temperature dependence shows characteristic features, but does not follow any simple form. Systematic variation in the TRM with cooling field and composition is apparent. The time dependence of the TRM is fit using a stretched exponential decay form. Systematic variations in the fit parameters with temperature, cooling field, and composition emerge. For low to moderate temperatures, the TRM is found to scale according to T log10(t/τ0), with τ0~10-12-10-13 s. For x=0.30 and 0.50, strong and weak irreversibility lines are determined. The former conform better to a recent prediction for the short-range three-dimensional Ising spin glass, τg~h0.53, than to the DeAlmeida-Thouless mean-field form τg~h2/3 best-fit exponents are slightly less than 0.53. For the weak irreversibility lines, the dependence of τg on field is much weaker than the Gabay-Toulouse form τg~h2. The presence of strong random anisotropy is a

  8. Exchange bias and spin glass behavior in biphasic NiFe2O4/NiO thin films

    Science.gov (United States)

    Pebley, Andrew C.; Fuks, Preston E.; Pollock, Tresa M.; Gordon, Michael J.

    2016-12-01

    Magnetic exchange bias and coercivity of nanogranular NiFe2O4/NiO thin films, prepared using flow-stabilized microplasmas and post-deposition annealing, have been investigated as a function of ferrimagnet/antiferromagnet phase fraction, grain size, and temperature. Exchange bias (EB) and vertical shifts in hysteresis loops observed in the as-deposited and low-T annealed (≤600 °C) films were attributed to exchange coupling between nanocrystalline NiFe2O4 (~8-10 nm) and a structurally-disordered spin glass (SG)-like phase. At higher annealing temperature (850 °C), the observed EB was found to arise from exchange coupling between NiFe2O4 and NiO, rather than a SG phase, most likely due to reduction of structurally-disordered interfaces and a substantial increase in NiFe2O4 grain size (~26 nm).

  9. Spin-glass, antiferromagnetism and Kondo behavior in Ce2Au1-CoSi3 alloys

    Indian Academy of Sciences (India)

    Subham Majumdar; E V Sampathkumaran; St Berger; M Della Mea; H Michor; E Bauer; M Brando; J Hemberger; A Loidl

    2002-05-01

    Recently, the solid solution Ce2Au1-CoSi3 has been shown to exhibit many magnetic anomalies associated with the competition between magnetic ordering and the Kondo effect. Here we report high pressure electrical resistivity of Ce2AuSi3, ac susceptibility () and magnetoresistance of various alloys of this solid solution in order to gain better knowledge of the magnetism of these alloys. High pressure resistivity behavior is consistent with the proposal that Ce2AuSi3 lies at the left-hand side of the maximum in Doniach’s magnetic phase diagram. The ac data reveal that there are in fact two magnetic transitions, one at 2 K and the other at 3 K for this compound, both of which are spin-glass-like. However, as the Co concentration is increased, antiferromagnetism is stabilized for intermediate compositions before attaining non-magnetism for the Co end member.

  10. Insulating and metallic spin glass in Ni-doped KxFe2-ySe2 single crystals

    Science.gov (United States)

    Ryu, Hyejin; Abeykoon, Milinda; Wang, Kefeng; Lei, Hechang; Lazarevic, N.; Warren, J. B.; Bozin, E. S.; Popovic, Z. V.; Petrovic, C.

    2015-05-01

    We report electron doping effects by Ni in KxFe2-δ -yNiySe2(0.06 ≤y ≤1.44 ) single-crystal alloys. A rich ground-state phase diagram is observed. A small amount of Ni (˜4 %) suppressed superconductivity below 1.8 K, inducing insulating spin-glass magnetic ground state for higher Ni content. With further Ni substitution, metallic resistivity is restored. For high Ni concentration in the lattice the unit cell symmetry is high symmetry I 4 /m m m with no phase separation whereas both I 4 /m +I 4 /m m m space groups were detected in the phase separated crystals when concentration of Ni < Fe. The absence of superconductivity coincides with the absence of crystalline Fe vacancy order.

  11. Spin-glass transition in Ni carbide single crystal nanoparticles with Ni3C − type structure

    Directory of Open Access Journals (Sweden)

    S. Fujieda

    2016-05-01

    Full Text Available Hexagonal shaped nanoparticles about 60 nm in size were successfully synthesized in tetraethylene glycol solution containing polyvinylpyrrolidone. By the analysis of the electron diffraction pattern, these were identified as a single crystal of Ni carbide with Ni3C − type structure. Their magnetization curve at 5 K was not completely saturated under a magnetic field of 5 T. The thermomagnetization curves after zero-field cooling and after field cooling exhibited the magnetic cooling effect at low temperatures. Furthermore, the 2nd order nonlinear term of AC magnetic susceptibility exhibited a negative divergence at about 17 K. It is concluded that Ni carbide single crystal nanoparticles with the Ni3C − type structure exhibit spin-glass transition at low temperatures.

  12. Perpendicular Magnetic Anisotropy and Spin Glass-like Behavior in Molecular Beam Epitaxy Grown Chromium Telluride Thin Films.

    Science.gov (United States)

    Roy, Anupam; Guchhait, Samaresh; Dey, Rik; Pramanik, Tanmoy; Hsieh, Cheng-Chih; Rai, Amritesh; Banerjee, Sanjay K

    2015-04-28

    Reflection high-energy electron diffraction (RHEED), scanning tunneling microscopy (STM), vibrating sample magnetometry, and other physical property measurements are used to investigate the structure, morphology, magnetic, and magnetotransport properties of (001)-oriented Cr2Te3 thin films grown on Al2O3(0001) and Si(111)-(7×7) surfaces by molecular beam epitaxy. Streaky RHEED patterns indicate flat smooth film growth on both substrates. STM studies show the hexagonal arrangements of surface atoms. Determination of the lattice parameter from the atomically resolved STM image is consistent with the bulk crystal structures. Magnetic measurements show the film is ferromagnetic, having a Curie temperature of about 180 K, and a spin glass-like behavior was observed below 35 K. Magnetotransport measurements show the metallic nature of the film with a perpendicular magnetic anisotropy along the c-axis.

  13. Spin glass behavior in the Dy{sub 3-x}Y{sub x}TaO{sub 7} (0≤x≤1) system

    Energy Technology Data Exchange (ETDEWEB)

    Gomez-Garcia, J. Francisco [Departamento de Física y Química Teórica, Facultad de Química, Universidad Nacional Autónoma de México, Av. Universidad 3000, Coyoacán, México D. F. 04510 (Mexico); Escudero, Roberto [Departamento de Materia Condensada y Criogenia, Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Av. Universidad 3000, Coyoacán, México D. F. 04510 (Mexico); Tavizon, Gustavo, E-mail: gtavizon@unam.mx [Departamento de Física y Química Teórica, Facultad de Química, Universidad Nacional Autónoma de México, Av. Universidad 3000, Coyoacán, México D. F. 04510 (Mexico)

    2014-09-15

    Several x-compositions of the polycrystalline Dy{sub 3−x}Y{sub x}TaO{sub 7} system, crystallizing in the weberite-type structure, were synthesized and structurally characterized using Rietveld refinements based on X-ray diffraction data. In previous magnetic characterization of Dy{sub 3}TaO{sub 7} (x=0), with the same crystal structure, an antiferromagnetic transition at T=2.3 K has been assigned to this compound. On the basis of DC and AC magnetic susceptibilities analyses, we show in this work that all compounds in the range of 0≤x≤1.0 exhibit a spin glass behavior. The nature of the spin glass behavior in Dy{sub 3−x}Y{sub x}TaO{sub 7}, can be attributed to the highly frustrated antiferromagnetic interaction of the Dy{sup 3+} sublattice and to the Dy{sup 3+}–Dy{sup 3+} distorted tetrahedra array in the weberite-type structure of this system. By fitting AC susceptibility data, using dynamical scaling theory equations, we conclude that a cluster spin glass is present in Dy{sub 3−x}Y{sub x}TaO{sub 7} in the low temperature range. Depending on the x-composition, T{sub g}∼2.2–3.2 K. In the range 15–300 K the system obeys a Curie–Weiss magnetic behavior. - Graphical abstract: Weberite-type crystal structure of the Dy{sub 3−x}Y{sub x}TaO{sub 7} compounds. In this structure the magnetic sublattice is formed by Dy{sup 3+} cations in an arrangement of distorted tetrahedra at the second-nearest neighbor site; this arrangement suggests geometric frustration that leads to a spin glass behavior. - Highlights: • Spin glass of Dy{sub 3−x}Y{sub x}TaO{sub 7} is associated to highly frustrated AFM interaction. • Quasi-one-dimensional feature of the crystal structure. • Suggest the existence of a cluster spin glass in Dy{sub 3−x}Y{sub x}TaO{sub 7}. • Dy{sub 3−x}Y{sub x}TaO{sub 7} system (x=0.33, 0.66, and 1.0) also display spin glass behavior.

  14. Large magnetoresistance and spin glass behavior of nanocrystalline La0.48Ca0.52MnO3 compound at low temperature

    Science.gov (United States)

    Das, Kalipada; Das, I.

    2017-10-01

    In this present study we report the large magnetoresistance and spin glass behavior of nanocrystalline La0.48Ca0.52MnO3 compound having average particle size 25 nm. Our experimental study reveals that in contrast to the bulk counterpart, the charge ordered antiferromagnetic ground state of the compound is totally suppressed and ferromagnetism part predominant. In addition to that, a spin glass like transition appears at the low temperature (∼42 K). Such glassy nature of the frozen spins influence the magnetoresistive properties of this compound also. Low field magnetoresistance at the low temperature of this compound is analyzed considering the correlation between the ferromagnetic clusters formed inside the grains.

  15. Spin Glass Order by Antisite Disorder in the Highly Frustrated Spinel Oxide CoAl2O4

    Science.gov (United States)

    Hanashima, Kentaro; Kodama, Yuta; Akahoshi, Daisuke; Kanadani, Chikahide; Saito, Toshiaki

    2013-02-01

    We experimentally studied the effects of the intersite mixing disorder between the A-site and B-site on the magnetic properties of the highly frustrated spinel oxide CoAl2O4 by measuring DC and AC susceptibilities. We controlled the inversion parameter η systematically from 0.0467 to 0.153 for (Co1-η Alη)[Al2-ηCoη]O4 by changing the heat treatment condition of the sample preparation. For η≤ 0.0643, no magnetic transition is observed down to 2 K, indicating a spin liquid (SL) regime for η≤ 0.0643, whereas for η≥ 0.101, a spin glass (SG) transition emerges at about Tg = 4.5 K, which is almost independent of η. In addition, the coefficient of the H--Tg relation is fairly large compared with that of a conventional SG. Our results suggest that some degrees of additional exchange randomness and local distortion by the quenched antisite disorder lead to degeneracy breaking in the SL state and induce SG order.

  16. Highly optimized simulations on single- and multi-GPU systems of the 3D Ising spin glass model

    Science.gov (United States)

    Lulli, M.; Bernaschi, M.; Parisi, G.

    2015-11-01

    We present a highly optimized implementation of a Monte Carlo (MC) simulator for the three-dimensional Ising spin-glass model with bimodal disorder, i.e., the 3D Edwards-Anderson model running on CUDA enabled GPUs. Multi-GPU systems exchange data by means of the Message Passing Interface (MPI). The chosen MC dynamics is the classic Metropolis one, which is purely dissipative, since the aim was the study of the critical off-equilibrium relaxation of the system. We focused on the following issues: (i) the implementation of efficient memory access patterns for nearest neighbours in a cubic stencil and for lagged-Fibonacci-like pseudo-Random Numbers Generators (PRNGs); (ii) a novel implementation of the asynchronous multispin-coding Metropolis MC step allowing to store one spin per bit and (iii) a multi-GPU version based on a combination of MPI and CUDA streams. Cubic stencils and PRNGs are two subjects of very general interest because of their widespread use in many simulation codes.

  17. Large area, screen printed silicon solar cells with selective emitter made by laser overdoping and RTA spin-on glasses

    Energy Technology Data Exchange (ETDEWEB)

    Besi-Vetrella, U.; Pirozzi, L.; Salza, E. [ENEA Casaccia, Roma (Italy); Ginocchietti, G.; Ferrazza, F. [Eurosolare, Roma (Italy); Ventura, L.; Slaoui, A.; Muller, J.C. [CNRS, Strasbourg (France)

    1997-12-31

    In this paper the authors describe their work on a new solar cells fabrication process, based on the use of Rapid Thermal Diffusion (RTD) from spin-on techniques, laser assisted treatments to get selective emitter structures, and screen-printing. The homogeneous lightly doped emitter is first made by rapid thermal diffusion from a P-doped Spin-On Glass (SOG) film. Laser overdoping of contact regions follows, to form the selective emitter structure, by writing the grid pattern using a laser beam. Finally, screen-printing is used to get the contacts; proper solutions have been developed for optical realignment to laser pattern, with a resolution of about 10 microns. The authors have first prepared several batches of small area solar cells, made by using these processes separately, with the aim to study the influence of the main laser and dopant parameters on cell performances. A further step has been to use all the processes together. Large area devices preparation is in progress.

  18. Numerically exact correlations and sampling in the two-dimensional Ising spin glass.

    Science.gov (United States)

    Thomas, Creighton K; Middleton, A Alan

    2013-04-01

    A powerful existing technique for evaluating statistical mechanical quantities in two-dimensional Ising models is based on constructing a matrix representing the nearest-neighbor spin couplings and then evaluating the Pfaffian of the matrix. Utilizing this technique and other more recent developments in evaluating elements of inverse matrices and exact sampling, a method and computer code for studying two-dimensional Ising models is developed. The formulation of this method is convenient and fast for computing the partition function and spin correlations. It is also useful for exact sampling, where configurations are directly generated with probability given by the Boltzmann distribution. These methods apply to Ising model samples with arbitrary nearest-neighbor couplings and can also be applied to general dimer models. Example results of computations are described, including comparisons with analytic results for the ferromagnetic Ising model, and timing information is provided.

  19. High-dimensional Gaussian fields with isotropic increments seen through spin glasses

    CERN Document Server

    Klimovsky, Anton

    2011-01-01

    We study the free energy of a particle in (arbitrary) high-dimensional Gaussian random potentials with isotropic increments. We prove a computable saddle-point variational representation in terms of a Parisi-type functional for the free energy in the infinite-dimensional limit. The proofs are based on the techniques developed in the course of the rigorous analysis of the Sherrington-Kirkpatrick model with vector spins.

  20. Observation of exchange bias and spin-glass-like ordering in -Fe2.8Cr0.2N nanoparticles

    Indian Academy of Sciences (India)

    N S Gajbhiye; Sayan Bhattacharyya; Sachil Sharma

    2008-02-01

    Nanoparticles of -Fe2.8Cr0.2N system exhibit the exchange bias phenomenon due to the exchange coupling of the spins of the antiferromagnetic (AF) oxide/oxynitride surface layer and the ferromagnetic (FM) nitride core. Exchange bias is observed at 10 K both in the absence and presence of cooling field. Due to the interface disorder, a mixture of parallel and anti-parallel/perpendicular coupling of the AF and FM spins is observed. The roughness of AF-FM interface induces disorder due to the random exchange anisotropy. The saturation magnetization is also found to be drastically lowered as compared to parent -Fe3N. Below 58 K, the broad peak (E ≅ f) in zero-field cooled (ZFC) magnetization curves indicates the presence of unidirectional anisotropy and spin-glass-like ordering, that arises from the freezing of localized frustrated spins.

  1. Real-space renormalization for the finite temperature statics and dynamics of the Dyson long-ranged ferromagnetic and spin-glass models

    Science.gov (United States)

    Monthus, Cécile

    2016-04-01

    The finite temperature dynamics of the Dyson hierarchical classical spins models is studied via real-space renormalization rules concerning the couplings and the relaxation times. For the ferromagnetic model involving long-ranged coupling J(r)\\propto {{r}-1-σ} in the region 1/2mean-field-like thermal ferromagnetic-paramagnetic transition, the RG flows are explicitly solved: the characteristic relaxation time τ (L) follows the critical power-law τ (L)\\propto {{L}{{z\\text{c}}(σ )}} at the phase transition and the activated law \\ln τ (L)\\propto {{L}\\psi} with \\psi =1-σ in the ferromagnetic phase. For the spin-glass model involving random long-ranged couplings of variance \\overline{{{J}2}(r)}\\propto {{r}-2σ} in the region 2/3mean-field-like thermal spin-glass-paramagnetic transition, the coupled RG flows of the couplings and of the relaxation times are studied numerically: the relaxation time τ (L) follows some power-law τ (L)\\propto {{L}{{z\\text{c}}(σ )}} at criticality and the activated law \\ln τ (L)\\propto {{L}\\psi} in the spin-glass phase with the dynamical exponent \\psi =1-σ =θ coinciding with the droplet exponent governing the flow of the couplings J(L)\\propto {{L}θ} .

  2. Composition-driven spin glass to ferromagnetic transition in the quasicrystal approximant Au-Al-Gd

    Science.gov (United States)

    Ishikawa, A.; Hiroto, T.; Tokiwa, K.; Fujii, T.; Tamura, R.

    2016-01-01

    We investigated the composition dependence of the magnetic susceptibility of the quasicrystal approximant Au-Al-Gd. A composition-driven ferromagnetic transition is observed in a quasicrystal approximant, which is attributed to the Ruderman-Kittel-Kasuya-Yosida (RKKY) oscillation via a variation in the Fermi wave vector. The ferromagnetic transition is most simply understood as a result of the close matching of the nearest and second-nearest spin distances with the maximum positions of the RKKY potential. The present work provides an idea that allows us to tailor the magnetic order via the electron concentration in quasicrystal approximants as well as in quasicrystals.

  3. 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

    2003-01-01

    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.

  4. Structural and magnetic properties of Ni78Fe22 thin films sandwiched between low-softening-point glasses and application in spin devices

    Science.gov (United States)

    Misawa, Takahiro; Mori, Sumito; Komine, Takashi; Fujioka, Masaya; Nishii, Junji; Kaiju, Hideo

    2016-12-01

    We investigate the structural and magnetic properties of Ni78Fe22 thin films sandwiched between low-softening-point (LSP) glasses, which can be used in spin quantum cross (SQC) devices utilizing stray magnetic fields generated from magnetic thin-film edges. We also calculate the stray magnetic field generated between the two edges of Ni78Fe22 thin-film electrodes in SQC devices and discuss the applicability to spin-filter devices. Using the established fabrication technique, we successfully demonstrate the formation of LSP-glass/Ni78Fe22/LSP-glass structures with smooth and clear interfaces. The coercivity of the Ni78Fe22 thin films is enhanced from 0.9 to 103 Oe by increasing the applied pressure from 0 to 1.0 MPa in the thermal pressing process. According to the random anisotropy model, the enhancement of the coercivity is attributed to the increase in the crystal grain size. The stray magnetic field is also uniformly generated from the Ni78Fe22 thin-film edge in the direction perpendicular to the cross section of the LSP-glass/Ni78Fe22/LSP-glass structures. Theoretical calculation reveals that a high stray field of approximately 5 kOe is generated when the distance between two edges of the Ni78Fe22 thin-film electrodes is less than 5 nm and the thickness of Ni78Fe22 is greater than 20 nm. These experimental and calculation results indicate that Ni78Fe22 thin films sandwiched between LSP glasses are useful as electrodes for SQC devices, serving as spin-filter devices.

  5. Glass-like recovery of antiferromagnetic spin ordering in a photo-excited manganite Pr0.7Ca0.3MnO3

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, S. Y.; Langner, M. C.; Zhu, Y.; Chuang, Y. -D.; Rini, M.; Glover, T. E.; Hertlein, M. P.; Gonzalez, A.G. Cruz; Tahir, N.; Tomioka, Y.; Tokura, Y.; Hussain, Z.; Schoenlein, R. W.

    2014-01-16

    Electronic orderings of charges, orbitals and spins are observed in many strongly correlated electron materials, and revealing their dynamics is a critical step toward understanding the underlying physics of important emergent phenomena. Here we use time-resolved resonant soft x-ray scattering spectroscopy to probe the dynamics of antiferromagnetic spin ordering in the manganite Pr0:7Ca0:3MnO3 following ultrafast photo-exitation. Our studies reveal a glass-like recovery of the spin ordering and a crossover in the dimensionality of the restoring interaction from quasi-1D at low pump fluence to 3D at high pump fluence. This behavior arises from the metastable state created by photo-excitation, a state characterized by spin disordered metallic droplets within the larger charge- and spin-ordered insulating domains. Comparison with time-resolved resistivity measurements suggests that the collapse of spin ordering is correlated with the insulator-to-metal transition, but the recovery of the insulating phase does not depend on the re-establishment of the spin ordering.

  6. Spin glass behavior in nanogranular La{sub 0.25}Ca{sub 0.75}MnO{sub 3} manganites

    Energy Technology Data Exchange (ETDEWEB)

    Fernández-Martínez, Antoni [Grup de Magnetisme, Dept. Física Fonamental, Facultat de Física, Universitat de Barcelona, Martí i Franquès 1, planta 4, edifici nou, 08028 Barcelona (Spain); Institut de Nanociència i Nanotecnologia IN" 2UB, Universitat de Barcelona, Martí i Franquès 1, planta 3, edifici nou, 08028 Barcelona (Spain); García-Santiago, Antoni, E-mail: agarciasan@ub.edu [Grup de Magnetisme, Dept. Física Fonamental, Facultat de Física, Universitat de Barcelona, Martí i Franquès 1, planta 4, edifici nou, 08028 Barcelona (Spain); Institut de Nanociència i Nanotecnologia IN" 2UB, Universitat de Barcelona, Martí i Franquès 1, planta 3, edifici nou, 08028 Barcelona (Spain); Hernàndez, Joan Manel [Grup de Magnetisme, Dept. Física Fonamental, Facultat de Física, Universitat de Barcelona, Martí i Franquès 1, planta 4, edifici nou, 08028 Barcelona (Spain); Institut de Nanociència i Nanotecnologia IN" 2UB, Universitat de Barcelona, Martí i Franquès 1, planta 3, edifici nou, 08028 Barcelona (Spain); Zhang, Tao [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China)

    2014-06-01

    The magnetic properties of two nanogranular La{sub 0.25}Ca{sub 0.75}MnO{sub 3} manganites with different average grain sizes have been studied. Besides the well-known exchange bias effect and the appearance of ferromagnetic clusters in the grains of both samples, the results show the occurrence of an antiferromagnetic transition and spin-glass properties. Both samples are described as core–shell magnetic systems, whose main difference is found in the interface between the outer ferromagnetic and the inner antiferromagnetic phases of the grains. - Highlights: • Nanogranular manganites show antiferromagnetism in magnetic measurements. • Exchange bias effect was observed in magnetic hysteresis cycles. • Spin-glass properties were detected at low temperatures. • A core-shell model was applied to describe the results in both samples. • These features have nothing to do with usual properties of nanoparticle manganites.

  7. Caracterización de la aleación (Fe0,65Ni0,35)1−xMnx en su fase spin glass

    OpenAIRE

    Acero Omaña, Anggie Maricel

    2012-01-01

    Se realizó la síntesis y caracterización de la aleación (Fe0;65Ni0;35)1−xMnx, la cual presenta varias fases magnéticas con la variación de la concentración de Mn, entre las que se encuentra la de Spin Glass. Se trabajó en el rango de concentraciones entre 10 y 20% de Mn, intervalo donde ha sido reportado un comportamiento spin glass. De mediciones de difracción de rayos x, se encontró que para este rango de concentraciones de Mn la estructura cristalográfica de las muestras permanece invarian...

  8. The Sherrington-Kirkpatrick spin glass model in the presence of a random field with a joint Gaussian probability density function for the exchange interactions and random fields

    Science.gov (United States)

    Hadjiagapiou, Ioannis A.

    2014-03-01

    The magnetic systems with disorder form an important class of systems, which are under intensive studies, since they reflect real systems. Such a class of systems is the spin glass one, which combines randomness and frustration. The Sherrington-Kirkpatrick Ising spin glass with random couplings in the presence of a random magnetic field is investigated in detail within the framework of the replica method. The two random variables (exchange integral interaction and random magnetic field) are drawn from a joint Gaussian probability density function characterized by a correlation coefficient ρ. The thermodynamic properties and phase diagrams are studied with respect to the natural parameters of both random components of the system contained in the probability density. The de Almeida-Thouless line is explored as a function of temperature, ρ and other system parameters. The entropy for zero temperature as well as for non zero temperatures is partly negative or positive, acquiring positive branches as h0 increases.

  9. Fragility of the spin-glass-like collective state to a magnetic field in an interacting Fe-C nanoparticle system

    DEFF Research Database (Denmark)

    Jönsson, P. E.; Felton, S.; Svedlindh, P.

    2001-01-01

    The effect of applied magnetic fields on the collective nonequilibrium dynamics of a strongly interacting Fe-C nanoparticle system has been investigated. It is experimentally shown that the magnetic aging diminishes to finally disappear for fields of moderate strength. The field needed to remove ...... the observable aging behavior increases with decreasing temperature. The same qualitative behavior is observed in an amorphous metallic spin glass (Fe0.15Ni0.85)(75)P16B6Al3....

  10. Spin-glass-like behaviour and positive magnetoresistance in oxygen deficient La2/3Ca1/3MnO3-δ thin films

    Institute of Scientific and Technical Information of China (English)

    Zhang Fu-Chang; Chen Wei-Ran; Gong Wei-Zhi; Xu Bo; Qiu Xiang-Gang; Zhao Bai-Ru

    2004-01-01

    The magnetism and magnetoresistance (MR) in a series of oxygen-deficient La2/3Ca1/3MnO3_δ (LCMO) thin films have been investigated. Compared with the films with stoichiometric oxygen concentration, the oxygen-deficient LCMO thin films show a spin-glass-like behaviour at low temperatures, and a positive MR effect above the metal-insulator transition temperature. The mechanism of such unusual phenomena is discussed.

  11. The three-dimensional Ising spin glass in an external magnetic field: the role of the silent majority

    Science.gov (United States)

    Baity-Jesi, M.; Baños, R. A.; Cruz, A.; Fernandez, L. A.; Gil-Narvion, J. M.; Gordillo-Guerrero, A.; Iñiguez, D.; Maiorano, A.; Mantovani, F.; Marinari, E.; Martin-Mayor, V.; Monforte-Garcia, J.; Muñoz Sudupe, A.; Navarro, D.; Parisi, G.; Perez-Gaviro, S.; Pivanti, M.; Ricci-Tersenghi, F.; Ruiz-Lorenzo, J. J.; Schifano, S. F.; Seoane, B.; Tarancon, A.; Tripiccione, R.; Yllanes, D.

    2014-05-01

    We perform equilibrium parallel-tempering simulations of the 3D Ising Edwards-Anderson spin glass in a field, using the Janus computer. A traditional analysis shows no signs of a phase transition. However, we encounter dramatic fluctuations in the behaviour of the model: averages over all the data only describe the behaviour of a small fraction of the data. Therefore, we develop a new approach to study the equilibrium behaviour of the system, by classifying the measurements as a function of a conditioning variate. We propose a finite-size scaling analysis based on the probability distribution function of the conditioning variate, which may accelerate the convergence to the thermodynamic limit. In this way, we find a non-trivial spectrum of behaviours, where some of the measurements behave as the average, while the majority show signs of scale invariance. As a result, we can estimate the temperature interval where the phase transition in a field ought to lie, if it exists. Although this would-be critical regime is unreachable with present resources, the numerical challenge is finally well posed.

  12. Theoretical Studies of the Spin Hamiltonian Parameters and Local Distortions for Cu2+ in Alkaline Earth Lead Zinc Phosphate Glasses

    Science.gov (United States)

    Wang, Bo-Kun; Wu, Shao-Yi; Yuan, Zi-Yi; Liu, Zi-Xuan; Jiang, Shi-Xin; Liu, Zheng; Yao, Zi-Jian; Teng, Bao-Hua; Wu, Ming-He

    2016-08-01

    The spin Hamiltonian parameters and local structures are theoretically studied for Cu2+-doped alkaline earth lead zinc phosphate (RPPZ, R=Mg, Ca, Sr, and Ba) glasses based on the high-order perturbation calculations for a tetragonally elongated octahedral 3d9 cluster. The relative elongation ratios are found to be ρ≈3.2%, 4.4%, 4.6%, and 3.3% for R=Mg, Ca, Sr, and Ba, respectively, because of the Jahn-Teller effect. The whole decreasing crystal-field strength Dq and orbital reduction factor k from Mg to Sr are ascribed to the weakening electrostatic coulombic interactions and the increasing probability of productivity of nonbridge oxygen (and hence increasing Cu2+-O2- electron cloud admixtures) under PbO addition, respectively, with increasing alkali earth ionic radius. The anomalies (the largest Dq and the next highest k among the systems) for R=Ba are attributed to the cross linkage of this large cation in the network. The overall increasing order (Mg≤Bacontaining copper dopants.

  13. SrFe{sub 0.9}Ti{sub 0.1}O{sub 3−δ}: A cluster spin glass

    Energy Technology Data Exchange (ETDEWEB)

    Sendil Kumar, A. [School of Physics, University of Hyderabad, Hyderabad 500 046 (India); Babu, P.D. [UGC-DAE Consortium for Scientific Research, R-5 Shed, B.A.R.C, Mumbai 400 085 (India); Srinath, S., E-mail: sssp@uohyd.ernet.in [School of Physics, University of Hyderabad, Hyderabad 500 046 (India)

    2014-03-01

    Graphical abstract: - Highlights: • Prepared SrFe{sub 0.9}Ti{sub 0.1}O{sub 3−δ} is in nanocrystalline form. • Arrott plot shows absence of spontaneous magnetization which rules out the possibility of long range ferromagnetic order. • AC susceptibility data is evidence of cluster spin glass. • There is no magnetic Bragg's reflection. • By substituting Ti{sup 4+}, helical antiferromagetic SrFeO{sub 3} is transformed to a cluster spin glass. - Abstract: The magnetic ground state of nanocrystalline SrFe{sub 0.9}Ti{sub 0.1}O{sub 3−δ} system has been investigated from 2 K to 300 K using AC Susceptibilty (ACS), magnetization and neutron diffraction measurements. The cusp in the temperature dependent magnetization and dispersion below T{sub max} (the temperature at which the maximum susceptibility is observed) in real part of ac susceptibility with frequency is observed. Arrott plot shows the lack of M{sub S} (spontaneous magnetization) down to 2 K, and the non-occurrence of magnetic Bragg reflections below the T{sub max} in neutron diffraction measurements, indicates the absence of long range ferro and antiferromagnetic order. The frequency dependence of T{sub max} obeys Vögel–Fulcher model establishing the cluster spin glass behavior in this system.

  14. Interfacial Spin Glass State and Exchange Bias in the Epitaxial La0.7Sr0.3MnO3/LaNiO3 Bilayer

    Science.gov (United States)

    Zhou, Guo-wei; Guan, Xiao-fen; Bai, Yu-hao; Quan, Zhi-yong; Jiang, Feng-xian; Xu, Xiao-hong

    2017-05-01

    We study the magnetic properties of an epitaxial growth bilayer composed of ferromagnetic La0.7Sr0.3MnO3 (LSMO) and paramagnetic LaNiO3 (LNO) on SrTiO3 (STO) substrates. We find that the stack order of the bilayer heterostructure plays a key role in the interfacial coupling strength, and the coupling at the LSMO(top)/LNO(bottom) interface is much stronger than that at the LNO(top)/LSMO(bottom). Moreover, a strong spin glass state has been observed at the LSMO/LNO interface, which is further confirmed by two facts: first, that the dependence of the irreversible temperature on the cooling magnetic field follows the Almeida-Thouless line and, second, that the relaxation of the thermal remnant magnetization can be fitted by a stretched exponential function. Interestingly, we also find an exchange bias effect at the LSMO/LNO bilayer below the spin glass freezing temperature, indicating that the exchange bias is strongly correlated with the spin glass state at its interface.

  15. Microstructure and microhardness of nanostructured Al-4.6Cu-Mn alloy ribbons

    Institute of Scientific and Technical Information of China (English)

    Zhong-wei Chen; Qin-ying Fan; Kai Zhao

    2015-01-01

    The microstructural characteristics and microhardness of nanostructured Al−4.6Cu−Mn ribbons produced by melt spinning were investigated using field-emission gun scanning electron microscopy, transmission electron microscopy, and hardness testing, and the results were compared to those of similar ribbons manufactured by direct-chill casting. It is shown that the nanostructure of the as-melt-spun ribbons consists ofα-Al dendrites with a secondary dendrite arm spacing of approximately 0.55−0.80μm and ultrafine eutectic crystals of a nanosized scale of approximately 100−200 nm on dendritic boundaries. The solidification time and cooling rate of 46-μm-thick ribbons were estimated to be 1.3 × 10−6 s and 4.04 × 106 K·s−1, respectively. At an aging temperature of 190°C, thecoherentθ″ phase in aged ribbons gradually transforms into nanoscaleθ′-phase platelets as the aging time is extended from 2 to 8 h; the rod-like morphology of the T (Al20Cu2Mn3) dispersoid with 120−160-nm diameter also forms, which results in peak aging hardness. The precipitation behaviors of aged ribbons cannot be changed at the high cooling rates of as-cast ribbons. However, a finer and more uniformly distributed microstructure and a supersaturated solid solution at a high cooling rate can shorten the time required to obtain a certain aging hardness before peak hardness.

  16. Surface spin glass and exchange bias effect in Sm0.5Ca0.5MnO3 manganites nano particles

    Directory of Open Access Journals (Sweden)

    S. K. Giri

    2011-09-01

    Full Text Available In this letter, we report that the charge/orbital order state of bulk antiferromagnetic Sm0.5Ca0.5MnO3 is suppressed and confirms the appearance of weak ferromagnetism below 65 K followed by a low temperature spin glass like transition at 41 K in its nano metric counterpart. Exchange anisotropy effect has been observed in the nano manganites and can be tuned by the strength of the cooling magnetic field (Hcool. The values of exchange fields (HE, coercivity (HC, remanence asymmetry (ME and magnetic coercivity (MC are found to strongly depend on cooling magnetic field and temperature. HE increases with increasing Hcool but for larger Hcool, HE tends to decrease due to the growth of ferromagnetic cluster size. Magnetic training effect has also been observed and it has been analyzed thoroughly using spin relaxation model. A proposed phenomenological core-shell type model is attributed to an exchange coupling between the spin-glass like shell (surrounding and antiferromagnetic core of Sm0.5Ca0.5MnO3 nano manganites mainly on the basis of uncompensated surface spins. Results suggest that the intrinsic phase inhomogeneity due to the surface effects of the nanostructured manganites may cause exchange anisotropy, which is of special interests for potential application in multifunctional spintronic devices.

  17. Mechanism of spin diffusion in electron spin resonance spectra of trapped electrons in aqueous glasses. Electron--Electron double resonance studies. [. gamma. -rays

    Energy Technology Data Exchange (ETDEWEB)

    Lin, D.P.; Kevan, L.

    1977-05-19

    Electron--electron double resonance (ELDOR) has been used to test the validity of the noninteracting spin packet model for inhomogeneously broadened ESR lines. For trapped electrons in 10M NaOD/D/sub 2/O glassy ice the saturation of field-swept ELDOR spectra fits the above mentioned model in contrast to earlier work on trapped electrons in protiated matrices. In the protiated matrix spin diffusion produces significant interaction between the spin packets. The difference between the protiated and deuterated matrices suggests that nuclear relaxation is the mechanism for spin diffusion. The deuterated matrices show no structure in frequency-swept ELDOR spectra due to deuteron spin--flip transitions whereas structure due to proton spin--flips is seen in protiated matrices.

  18. Reentrant spin-glass behavior and bipolar exchange-bias effect in “Sn” substituted cobalt-orthotitanate

    Energy Technology Data Exchange (ETDEWEB)

    Nayak, S.; Joshi, D. C.; Thota, S., E-mail: subhasht@iitg.ac.in [Department of Physics, Indian Institute of Technology, Guwahati 781039, Assam (India); Krautz, M.; Waske, A. [Institute for Complex Materials, IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany); Eckert, J. [Erich Schmid Institute of Materials Science, Jahnstrasse 12, A-8700 Leoben (Austria); Department Materials Physics, Montanuniversität Leoben, Jahnstrasse 12, A-8700 Leoben (Austria)

    2016-01-28

    We report the co-existence of longitudinal ferrimagnetic behavior with Néel temperature T{sub N} ∼ 46.1 K and reentrant transverse spin-glass state at 44.05 K in Tin (Sn) doped cobalt-orthotitanate (Co{sub 2}TiO{sub 4}). The ferrimagnetic ordering is resulting from different magnetic moments of Co{sup 2+} on the A-sites (3.87 μ{sub B}) and B-sites (5.069 μ{sub B}). The magnetic compensation temperature (T{sub COMP}) shifts from 31.74 K to 27.1 K when 40 at. % of “Sn{sup 4+}” substitutes “Ti{sup 4+}” at B-sites where the bulk-magnetization of two-sublattices balance each other. For T > T{sub N}, the dc-magnetic susceptibility (χ{sub dc} = M/H{sub dc}) fits well with the Néel's expression for the two-sublattice model with antiferromagnetic molecular field constants N{sub BB} ∼ 15.44, N{sub AB} ∼ 32.01, and N{sub AA} ∼ 20.88. The frequency dependence of ac-magnetic susceptibility χ{sub ac} data follows the Vogel-Fulcher law, and the power-law of critical slowing-down with “zν” = 6.01 suggests the existence of spin-clusters (where “z” and “ν” being dynamic critical-exponent and correlation length of critical-exponent, respectively). This system exhibits unusual hysteresis loops with large bipolar exchange-bias effect (H{sub EB} ∼ 13.6 kOe at 7 K) after zero-field cooling process from an un-magnetized state, and a dramatic collapse of remanence (M{sub R}) and coercive field (H{sub C}) across T{sub COMP}. The possible origins of such anomalous characteristics were discussed.

  19. Low-temperature formation of high-quality gate oxide by ultraviolet irradiation on spin-on-glass

    Science.gov (United States)

    Usuda, R.; Uchida, K.; Nozaki, S.

    2015-11-01

    Although a UV cure was found to effectively convert a perhydropolysilazane (PHPS) spin-on-glass film into a dense SiOx film at low temperature, the electrical characteristics were never reported in order to recommend the use of PHPS as a gate-oxide material that can be formed at low temperature. We have formed a high-quality gate oxide by UV irradiation on the PHPS film, and obtained an interface midgap trap density of 3.4 × 1011 cm-2 eV-1 by the UV wet oxidation and UV post-metallization annealing (PMA), at a temperature as low as 160 °C. In contrast to the UV irradiation using short-wavelength UV light, which is well known to enhance oxidation by the production of the excited states of oxygen, the UV irradiation was carried out using longer-wavelength UV light from a metal halide lamp. The UV irradiation during the wet oxidation of the PHPS film generates electron-hole pairs. The electrons ionize the H2O molecules and facilitate dissociation of the molecules into H and OH-. The OH- ions are highly reactive with Si and improve the stoichiometry of the oxide. The UV irradiation during the PMA excites the electrons from the accumulation layer, and the built-in electric field makes the electron injection into the oxide much easier. The electrons injected into the oxide recombine with the trapped holes, which have caused a large negative flat band voltage shift after the UV wet oxidation, and also ionize the H2O molecules. The ionization results in the electron stimulated dissociation of H2O molecules and the decreased interface trap density.

  20. Spin glass transition in the rhombohedral LiNi{sub 1/3}Mn{sub 1/3}Co{sub 1/3}O{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Bie, Xiaofei; Yang, Xu [Key Laboratory of Advanced Batteries Physics and Technology, Ministry of Education, College of Physics, Jilin University, Changchun 130012 (China); Han, Bing [College of Physics, Jilin University, Changchun 130012 (China); Chen, Nan; Liu, Lina; Wei, Yingjin; Wang, Chunzhong [Key Laboratory of Advanced Batteries Physics and Technology, Ministry of Education, College of Physics, Jilin University, Changchun 130012 (China); Chen, Hong [College of Physics, Beihua University, Jilin 132013 (China); Du, Fei, E-mail: dufei@jlu.edu.cn [Key Laboratory of Advanced Batteries Physics and Technology, Ministry of Education, College of Physics, Jilin University, Changchun 130012 (China); Chen, Gang [Key Laboratory of Advanced Batteries Physics and Technology, Ministry of Education, College of Physics, Jilin University, Changchun 130012 (China)

    2013-09-25

    Highlights: •The Rietveld analysis of XRD data reveals a single phase with rhombohedral structure. •Dc susceptibility data suggest a spin glass behavior at low T in the 333 compound. •The ac susceptibility measurements have been observed in the typical SG system. •Three models have been employed to study the behavior of the spin glass state. •Both geometrical frustration and disorder play important role in the formation of SG. -- Abstract: Layered LiNi{sub 1/3}Mn{sub 1/3}Co{sub 1/3}O{sub 2} has been synthesized by co-precipitation method, and the magnetic properties were comprehensively studied by dc and ac susceptibilities. The dc magnetization curves show the irreversibility and spin freezing behavior at 109 K and 9 K. The evolution of real and imaginary part of ac susceptibility under different frequencies indicates a spin glass transition at low temperature. Three models (the Néel–Arrhenius law, the Vogel–Fulcher law, and the power law) have been employed to study the relaxation behavior of the spin glass state. Both frustration and disorder play important role in the formation of spin glass.

  1. Investigation of the Spin-glass Regime Between the Antiferromagnetic and Superconducting Phases in Fe1+ySexTe1−x

    Energy Technology Data Exchange (ETDEWEB)

    Katayama, N.; Wen, J.; Ji, S.; Louca, D.; Lee, S.-H.; Fujita, M.; Sato, T.J.; Wen, J.S.; Xu, Z.J.; Gu, G.D.; Xu, G.; Lin, Z.W.; Enoki, M.; Chang, S.; Yamada, K.; Tranquada, J.M.

    2010-11-01

    Using bulk magnetization along with elastic and inelastic neutron scattering techniques, we have investigated the phase diagram of Fe{sub 1+y}Se{sub x}Te{sub 1-x} and the nature of magnetic correlations in three nonsuperconducting samples of Fe{sub 1.01}Se{sub 0.1}Te{sub 0.9}, Fe{sub 1.01}Se{sub 0.15}Te{sub 0.85}, and Fe{sub 1.02}Se{sub 0.3}Te{sub 0.7}. A cusp and hysteresis in the temperature dependence of the magnetization for the x=0.15 and 0.3 samples indicates spin-glass (SG) ordering below T{sub sg} = 23 K. Neutron scattering measurements indicate that the spin-glass behavior is associated with short-range spin density wave (SDW) ordering characterized by a static component and a low-energy dynamic component with a characteristic incommensurate wave vector of Q{sub m} = (0.46, 0, 0.50) and an anisotropy gap of -2.5 meV. Our high Q-resolution data also show that the systems undergo a glassy structural distortion that coincides with the short-range SDW order.

  2. Surface spin-glass, large surface anisotropy, and depression of magnetocaloric effect in La0.8Ca0.2MnO3 nanoparticles

    Science.gov (United States)

    Xi, S. B.; Lu, W. J.; Wu, H. Y.; Tong, P.; Sun, Y. P.

    2012-01-01

    The surface magnetic behavior of La0.8Ca0.2MnO3 nanoparticles was investigated. We observed irreversibility in high magnetic field. The surface spin-glass behavior as well as the high-field irreversibility is suppressed by increasing particle size while the freezing temperature TF does not change with particle size. The enhanced coercivity has been observed in the particles and we attributed it to the large surface anisotropy. We have disclosed a clear relationship between the particle size, the thickness of the shell, and the saturation magnetization of the particles. The large reduction of the saturation magnetization of the samples is found to be induced by the increase of nonmagnetic surface large since the thickness of the spin-disordered surface layer increases with a decrease in the particle size. Due to the reduction of the magnetization, the magnetocaloric effect (MCE) has been reduced by the decreased particle size since the nonmagnetic surface contributes little to the MCE. Based on the core-shell structure, large relative cooling powers RCP(s) of 180 J/kg and 471 J/kg were predicted for a field change of 2.0 T and 4.5 T, respectively, in the small particles with thin spin-glass layer. PMID:23319829

  3. Surface spin-glass, large surface anisotropy, and depression of magnetocaloric effect in La(0.8)Ca(0.2)MnO(3) nanoparticles.

    Science.gov (United States)

    Xi, S B; Lu, W J; Wu, H Y; Tong, P; Sun, Y P

    2012-12-15

    The surface magnetic behavior of La(0.8)Ca(0.2)MnO(3) nanoparticles was investigated. We observed irreversibility in high magnetic field. The surface spin-glass behavior as well as the high-field irreversibility is suppressed by increasing particle size while the freezing temperature T(F) does not change with particle size. The enhanced coercivity has been observed in the particles and we attributed it to the large surface anisotropy. We have disclosed a clear relationship between the particle size, the thickness of the shell, and the saturation magnetization of the particles. The large reduction of the saturation magnetization of the samples is found to be induced by the increase of nonmagnetic surface large since the thickness of the spin-disordered surface layer increases with a decrease in the particle size. Due to the reduction of the magnetization, the magnetocaloric effect (MCE) has been reduced by the decreased particle size since the nonmagnetic surface contributes little to the MCE. Based on the core-shell structure, large relative cooling powers RCP(s) of 180 J/kg and 471 J/kg were predicted for a field change of 2.0 T and 4.5 T, respectively, in the small particles with thin spin-glass layer.

  4. Triple-quantum two-dimentional {sup 27}Al magic-angle spinning nuclear magnetic resonance spectroscopic study of aluminosilicate and aluminate crystals and glasses

    Energy Technology Data Exchange (ETDEWEB)

    Baltisberger, J.H. [Berea College, KY (United States); Xu, Z.; Stebbins, J.F. [Stanford Univ., CA (United States); Wang, S.H.; Pines, A. [Lawrence Berkeley National Lab., CA (United States)

    1996-07-31

    A new two-dimensional magic-angle spinning NMR experiment using multiple-quantum coherence of half-integer quadrupolar nuclei was used to study {sup 27}Al sites in crystalline samples of leucite (KAlSi{sub 2}O{sub 6}), anorthite (CaAl{sub 2}Si{sub 2}O{sub 8}), and kyanite (Al{sub 2}SiO{sub 5}), as well as CaAl{sub 2}Si{sub 2}O{sub 8} glass and a magnesium aluminoborate glass. In the crystals, multiple sites are partially resolved and new results for isotropic chemical shifts and quadrupolar parameters are derived, using data collected at a single magnetic field. Data for both leucite and anorthite are consistent with previous results that correlate chemical shifts with mean intertetrahedral bond angle. Signal can be obtained from sites with quadrupolar coupling constants as large as 9 MHz, but intensities are reduced. In the aluminoborate glass, peaks for sites with different Al coordination numbers are well seperated. The lack of such features in CaAl{sub 2}Si{sub 2}O{sub 8} glass rules out the presence of significant quantities of AlO{sub 5} and AlO{sub 6} groups. 31 refs., 8 figs., 3 tabs.

  5. Spin-glass and variable range hopping quantum interference magnetoresistance in FeSr2Y1.3Ce0.7Cu2O10-x

    Science.gov (United States)

    Sambale, S.; Williams, G. V. M.; Stephen, J.; Chong, S. V.

    2014-12-01

    Electronic transport and magnetic measurements have been made on FeSr2Y1.3Ce0.7Cu2O10-x. We observe a spin-glass at ˜23 K and a magnetoresistance that reaches -22% at 8 T. The magnetoresistance is due to variable range hopping quantum interference where at low temperatures each hop is over a large number of scatterers. This magnetoresistance is negative at and above 5 K and can be described by the Nguen, Spivak, and Shklovskii (NSS) model. However, there is an increasingly positive contribution to the magnetoresistance for temperatures below 5 K that may be due to scattering from localized free spins during each hop that is not accounted for in the NSS model.

  6. Apparent specific heat of a spin glass ( Au Fe 6 at %) in presence of a remanent magnetization and associated energy and magnetization relaxations

    Science.gov (United States)

    Berton, A.; Chaussy, J.; Odin, J.; Peyrard, J.; Prejean, J. J.; Souletie, J.

    1981-01-01

    We present measurements of the relaxations of the remanent magnetization and of the energy flux on the same samples of Au Fe spin glass (4 at % and 6 at %) at several temperatures below the temperature T G of the susceptibility cusp. The observed relaxations can be expressed in terms of the unique composite variable T ℓnt/τ which implies the existence of thermally activated asymetrical double well potentials. A consequency of this observation is the existence of a time and temperature contribution to the specific heat which is investigated directly and compared with expectation.

  7. Spin glass behavior in a highly oxygen deficient Perovskite BaBiO.28Co0.72O2.2

    Energy Technology Data Exchange (ETDEWEB)

    Klimczuk, Thomasz W [Los Alamos National Laboratory; Zandbergen, H [DELFT UNIV.; Huang, Q [NIST CENTER FOR NEUTRON; Mcqueen, T [PRINCETON U.

    2008-01-01

    A highly oxygen deficient perovskite, BaBio.28Coo.n02.2, was synthesized by solid state reaction. The crystal structure was determined by neutron and x-ray powder diffraction. The material exhlbits semiconducting behavior with an energy gap of 1.8 eV. Magnetic susceptibility studies reveal spin-glass ordering, which may have its origin in the frustration caused by the presence of competing antiferromagnetic and ferromagnetic interactions. The electron diffraction study shows the existence of short range ordering in thls phase.

  8. Coexistence of Kondo and spin-glass behaviour in Ce{sub 4}Y{sub 3}Ni{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Trovarelli, O. [Centro Atomico Bariloche, Comision Nacional de Energia Atomica, 8400 S.C. de Bariloche (Argentina); Sereni, J.G. [Centro Atomico Bariloche, Comision Nacional de Energia Atomica, 8400 S.C. de Bariloche (Argentina); Schmerber, G. [Institut de Physique et Chimie des Materiaux de Strasbourg, Groupe d`Etude des Materiaux Metallique, 23 rue du Loess, 67037 Strasbourg (France); Kappler, J.P. [Institut de Physique et Chimie des Materiaux de Strasbourg, Groupe d`Etude des Materiaux Metallique, 23 rue du Loess, 67037 Strasbourg (France)

    1995-02-09

    Magnetic susceptibility {chi} and specific heat C{sub P} measurements on Ce{sub 4}Y{sub 3}Ni{sub 3} are presented. The temperature of the maximum of {chi}{sub ac}(T) and C{sub P}(T) shifts with frequency and applied field respectively, as expected for a spin glass (SG) system. The C{sub P} (T{yields}0) dependence corresponds to that of an anisotropic SG. According to the entropy gain two Ce atoms are involved in the SG contribution and two exhibit Kondo effect. ((orig.)).

  9. Spin glass behavior in LaCo1 -xRhxO3 (x =0.4 , 0.5, and 0.6)

    Science.gov (United States)

    Guo, H.; Manna, K.; Luetkens, H.; Hoelzel, M.; Komarek, A. C.

    2016-11-01

    We studied the magnetic ground state of Co/Rh-disordered LaCo1 -xRhxO3 (x =0.4 , 0.5, and 0.6) by means of powder neutron diffraction (PND), muon spin relaxation (μ SR ), ac susceptibility, isothermal magnetic relaxation, and heat capacity measurements. The dc magnetic susceptibility measurements exhibit a cusp around the freezing temperature Tf of all studied compounds. PND measurements show no indications of long-range magnetic ordering down to 4 K in all studied samples. μ SR experiments on these compounds show a peak in the muon spin relaxation rate around Tf. However, no spontaneous muon spin precession can be observed evidencing the short-range nature of the magnetic ordering. For the x =0.5 sample ac susceptibility measurements show that Tf shifts to higher temperatures with increasing frequency and becomes suppressed by a dc biasing field. All these observations indicate that the Co/Rh-disordered LaCo1 -xRhxO3 system is a spin glass for x =0.4 , 0.5, and 0.6.

  10. Structural features of spin-coated thin films of binary As{sub x}S{sub 100−x} chalcogenide glass system

    Energy Technology Data Exchange (ETDEWEB)

    Cook, J. [Austin Peay State University, Clarksville, TN 37075 (United States); Slang, S. [Faculty of Chemical Technology, University of Pardubice, 53210 Pardubice (Czech Republic); Golovchak, R. [Austin Peay State University, Clarksville, TN 37075 (United States); Jain, H. [International Materials Institute for New Functionality in Glass, Lehigh University, Bethlehem, PA 18015 (United States); Vlcek, M. [Faculty of Chemical Technology, University of Pardubice, 53210 Pardubice (Czech Republic); Kovalskiy, A., E-mail: kovalskyya@apsu.edu [Austin Peay State University, Clarksville, TN 37075 (United States)

    2015-08-31

    Spin-coating technology offers a convenient method for fabricating photostable chalcogenide glass thin films that are especially attractive for applications in IR optics. In this paper we report the structure of spin-coated As{sub x}S{sub 100−x} (x = 30, 35, 40) thin films as determined using high resolution X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, especially in relation to composition (i.e. As/S ratio) and preparation process variables. It was observed that As atoms during preparation have a tendency to precipitate out in close to stoichiometric compositions. The mechanism of bonding between the inorganic matrix and organic residuals is discussed based on the experimental data. A weak interaction between S ions and amine-based clusters is proposed as the basis of structural organization of the organic–inorganic interface. - Highlights: • As–S spin-coated chalcogenide thin films with different As/S were fabricated. • XPS measurements support the cluster-like structure of spin-coated films. • As{sub 2}O{sub 3} was confirmed as the composition of precipitate formed during dissolution. • Lack of As–As bonds explains the observed photostability of the thin films.

  11. Large magnetic cooling power involving frustrated antiferromagnetic spin-glass state in R2NiSi3(R =Gd ,Er )

    Science.gov (United States)

    Pakhira, Santanu; Mazumdar, Chandan; Ranganathan, R.; Giri, S.; Avdeev, Maxim

    2016-09-01

    The ternary intermetallic compounds Gd2NiSi3 and Er2NiSi3 are synthesized in chemically single phase, which are characterized using dc magnetization, ac magnetic susceptibility, heat capacity, and neutron diffraction studies. Neutron diffraction and heat capacity studies confirm that long-range magnetic ordering coexists with the frustrated glassy magnetic components for both compounds. The static and dynamical features of dc magnetization and frequency-dependent ac susceptibility data reveal that Gd2NiSi3 is a canonical spin-glass system, while Er2NiSi3 is a reentrant spin cluster-glass system. The spin freezing temperature merges with the long-range antiferromagnetic ordering temperature at 16.4 K for Gd2NiSi3 . Er2NiSi3 undergoes antiferromagnetic ordering at 5.4 K, which is slightly above the spin freezing temperature at 3 K. The detailed studies of nonequilibrium dynamical behavior, viz., the memory effect and relaxation behavior using different protocols, suggest that both compounds favor the hierarchical model over the droplet model. A large magnetocaloric effect is observed for both compounds. Maximum values of isothermal entropy change (-Δ SM ) and relative cooling power (RCP) are found to be 18.4 J/kg K and 525 J/kg for Gd2NiSi3 and 22.6 J/kg K and 540 J/kg for Er2NiSi3 , respectively, for a change in field from 0 to 70 kOe. The values of RCP are comparable to those of the promising refrigerant materials. A correlation between large RCP and magnetic frustration is discussed for developing new magnetic refrigerant materials.

  12. The evolution from long-range magnetic order to spin-glass behaviour in PrAu2(Si1- xGex)2

    Science.gov (United States)

    Krimmel, A.; Hemberger, J.; Kegler, C.; Nicklas, M.; Engelmayer, A.; Knebel, G.; Fritsch, V.; Reehuis, M.; Brando, M.; Loidl, A.

    1999-09-01

    We have studied the magnetic behaviour of PrAu2(Si1-xGex)2 by means of magnetic susceptibility, resistivity, and heat capacity measurements, and x-ray and neutron powder diffraction. All compounds are isostructural and crystallize in the well known ThCr2Si2-type structure. PrAu2Si2 shows the characteristic features of a canonical spin glass with a freezing temperature of TF = 3 K. Completely unexpectedly, on introducing/increasing the atomic disorder by alloying with Ge, the spin-glass transition is suppressed as is first evident from a slight decrease of the freezing temperature TF up to x = 0.10. Long-range magnetic order sets in for xicons/Journals/Common/ge" ALT="ge" ALIGN="TOP"/>0.12. Within the range 0.15icons/Journals/Common/le" ALT="le" ALIGN="TOP"/> xicons/Journals/Common/le" ALT="le" ALIGN="TOP"/>1, all compounds show the same simple AF-I-type antiferromagnetic structure with a monotonic increase of both the Néel temperature and the ordered magnetic moment for increasing Ge concentration. The magnetic phase diagram of PrAu2(Si1-xGex)2 is explained by the presence of weak disorder at a constant level at the Au sites. Clear indications of crystal-field effects have been observed.

  13. Nuclear Spin Lattice Relaxation and Conductivity Studies of the Non-Arrhenius Conductivity Behavior in Lithium Fast Ion Conducting Sulfide Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Benjamin Michael Meyer

    2003-05-31

    As time progresses, the world is using up more of the planet's natural resources. Without technological advances, the day will eventually arrive when these natural resources will no longer be sufficient to supply all of the energy needs. As a result, society is seeing a push for the development of alternative fuel sources such as wind power, solar power, fuel cells, and etc. These pursuits are even occurring in the state of Iowa with increasing social pressure to incorporate larger percentages of ethanol in gasoline. Consumers are increasingly demanding that energy sources be more powerful, more durable, and, ultimately, more cost efficient. Fast Ionic Conducting (FIC) glasses are a material that offers great potential for the development of new batteries and/or fuel cells to help inspire the energy density of battery power supplies. This dissertation probes the mechanisms by which ions conduct in these glasses. A variety of different experimental techniques give a better understanding of the interesting materials science taking place within these systems. This dissertation discusses Nuclear Magnetic Resonance (NMR) techniques performed on FIC glasses over the past few years. These NMR results have been complimented with other measurement techniques, primarily impedance spectroscopy, to develop models that describe the mechanisms by which ionic conduction takes place and the dependence of the ion dynamics on the local structure of the glass. The aim of these measurements was to probe the cause of a non-Arrhenius behavior of the conductivity which has been seen at high temperatures in the silver thio-borosilicate glasses. One aspect that will be addressed is if this behavior is unique to silver containing fast ion conducting glasses. more specifically, this study will determine if a non-Arrhenius correlation time, {tau}, can be observed in the Nuclear Spin Lattice Relaxation (NSLR) measurements. If so, then can this behavior be modeled with a new single

  14. Nuclear Spin Lattice Relaxation and Conductivity Studies of the Non-Arrhenius Conductivity Behavior in Lithium Fast Ion Conducting Sulfide Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, Benjamin Michael [Iowa State Univ., Ames, IA (United States)

    2003-01-01

    As time progresses, the world is using up more of the planet's natural resources. Without technological advances, the day will eventually arrive when these natural resources will no longer be sufficient to supply all of the energy needs. As a result, society is seeing a push for the development of alternative fuel sources such as wind power, solar power, fuel cells, and etc. These pursuits are even occurring in the state of Iowa with increasing social pressure to incorporate larger percentages of ethanol in gasoline. Consumers are increasingly demanding that energy sources be more powerful, more durable, and, ultimately, more cost efficient. Fast Ionic Conducting (FIC) glasses are a material that offers great potential for the development of new batteries and/or fuel cells to help inspire the energy density of battery power supplies. This dissertation probes the mechanisms by which ions conduct in these glasses. A variety of different experimental techniques give a better understanding of the interesting materials science taking place within these systems. This dissertation discusses Nuclear Magnetic Resonance (NMR) techniques performed on FIC glasses over the past few years. These NMR results have been complimented with other measurement techniques, primarily impedance spectroscopy, to develop models that describe the mechanisms by which ionic conduction takes place and the dependence of the ion dynamics on the local structure of the glass. The aim of these measurements was to probe the cause of a non-Arrhenius behavior of the conductivity which has been seen at high temperatures in the silver thio-borosilicate glasses. One aspect that will be addressed is if this behavior is unique to silver containing fast ion conducting glasses. more specifically, this study will determine if a non-Arrhenius correlation time, τ, can be observed in the Nuclear Spin Lattice Relaxation (NSLR) measurements. If so, then can this behavior be modeled with a new single

  15. Magnetic impurity doping induced spin-glass state and short-range zigzag order in the honeycomb iridate Na2IrO3

    Science.gov (United States)

    Cai, W. P.; Yan, Z. R.; Liu, R. M.; Qin, M. H.; Zeng, M.; Lu, X. B.; Gao, X. S.; Liu, J.-M.

    2017-10-01

    Based on the modified Heisenberg–Kitaev model, the effects of magnetic substitution on the magnetic properties of the honeycomb-lattice iridate Na2 IrO3 are studied using Monte Carlo simulations. It is observed that the long-range zigzag state of the original system is rather fragile and can be replaced by a spin-glass state even for small substitution, well consistent with the experimental observation in Ru-substituted samples (Mehlawat et al 2015 Phys. Rev. B 92 134412). Both the disordered Heisenberg and Kitaev interactions caused by the magnetic ion-doping are suggested to be responsible for the magnetic phase transitions in the system. More interestingly, a short-range zigzag order is suggested to survive above the freezing temperature even at high magnetic impurity doping levels.

  16. Interpretation of the spin glass behaviour of diluted magnetic semiconductors below the nearest-neighbour percolation threshold via realistic Monte Carlo simulations

    CERN Document Server

    Karaoulanis, D; Bacalis, N C

    2000-01-01

    We have performed Monte Carlo simulations of magnetic semiconductors above and below the nearest-neighbour percolation threshold (NNPT) using a classical Heisenberg Hamiltonian with up to third nearest-neighbour (nn) interactions. Large clusters were created allowing use of realistically low magnetic fields (10 G). Above NNPT our results, apart from confirming the existing picture of this class of materials, also show that the inclusion of the second and third (nn) interactions increases the frustration, thus making the transition temperature smaller and closer to experiment than calculated via the first nn interactions only. A physically plausible explanation is given. Below NNPT our results strongly support the validity of the hypothesis (D. Karaoulanis, J.P. Xanthakis, C. Papatriantafillou, J. Magn. Magn. Mater. 161 (1996) 231), that the experimentally observed susceptibility is the sum of two contributions: a paramagnetic one due to isolated magnetic clusters, and a spin-glass contribution due to an 'infi...

  17. Coexistence of antiferromagnetic and spin-glass behaviour in U{sub 3}Rh{sub 3}Sb{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Tran, V H; Bukowski, Z; Stepien-Damm, J; Zaleski, A J; Badurski, D; Gorzelniak, R; Sulkowski, Cz; Troc, R [W Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, PO Box 1410, P-50-950 Wroclaw (Poland)

    2005-06-15

    We report on single-crystal growth, crystal structural determination and magnetic, electrical resistivity and thermoelectric power measurements performed on a set of single crystals of U{sub 3}Rh{sub 3}Sb{sub 4}. The compound crystallizes in the cubic Y{sub 3}Au{sub 3}Sb{sub 4}-type structure. The ac susceptibility and dc magnetization both indicate that the compound undergoes a transition into a spin-glass state below 14.7 K. The resistivity shows a broad minimum at 30 K. The thermoelectric power is negative in the whole temperature range studied and exhibits an enhanced value of -32 {mu}V K{sup -1} at room temperature.

  18. Spin-Glass Behavior, Magnetic, and IR Spectroscopy Analysis of Multimetallic Compound Ni0.25Mn1.25[Fe(CN6]·6.1H2O

    Directory of Open Access Journals (Sweden)

    Qing Lin

    2015-01-01

    Full Text Available Multimetallic Prussian blue compound Ni0.25Mn1.25[Fe(CN6]·6.1H2O has been prepared by coprecipitation. The temperature-dependent magnetic susceptibilities show the magnet transition for the compound at 8.5 K. According to DC variable-temperature magnetic susceptibility paramagnetic Curie temperature θ is −9.32 K. The observed value of coercive field (Hc and the remanent magnetization (Mr for the compound are 0.32 KOe and 0.36 μB. According to study of zero-field-cooled (ZFC and field-cooled (FC magnetization curves and AC magnetization curves, there exists a spin-glass behaviour in the compound, which exhibits freezing temperature Tg=7.76 K, below magnetic transition TC=8.5 K; that glass behavior is termed “reentrant” spin glass.

  19. Origin of spin-glass and exchange bias in La1/3Sr2/3FeO3-γ nanoparticles

    Science.gov (United States)

    da Silva, R. B.; de Araújo, J. H.; Soares, J. M.; Machado, F. L. A.

    2014-03-01

    The structure and the magnetic properties of nanopowdered samples of La1/3Sr2/3FeO3-γ with average particles size d in the range of 67-367 nm prepared by a sol-gel method were investigated in detail. The samples were characterized by X-ray diffraction, scanning electron microscopy, specific heat, Mössbauer spectroscopy, ac susceptibility, and magnetization measurements. Exchange bias with vertical magnetization shift was found in all samples. Charge ordering and antiferromagnetism were observed close to 200 K for large particles (d ≥ 304 nm) samples, while for particles with intermediated and smaller values (d ≤ 156 nm) a cluster-glass like behaviour and a short range charge ordering were seen near 115 K and 200 K, respectively. The spin-glass like and exchange bias behaviour in nanopowdered samples of La1/3Sr2/3FeO3-γ are associated to compact Fe3+ antiferromagnetic (AF) clusters caused by an oxygen deficiency, which was found to be higher in the samples with the smallest average particles sizes. The effect of exchange bias and vertical magnetization shifts are explained by a simple model involving the interaction of one AF phase with a canted AF phase.

  20. Theoretical studies of the spin Hamiltonian parameters and local distortions for Cu{sup 2+} in alkaline earth lead zinc phosphate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Bo-Kun; Yuan, Zi-Yi; Liu, Zi-Xuan; Jiang, Shi-Xin; Liu, Zheng; Yao, Zi-Jian [University of Electronic Science and Technology of China, Chengdu (China). School of Yingcai Honors; Wu, Shao-Yi; Teng, Bao-Hua; Wu, Ming-He [University of Electronic Science and Technology of China, Chengdu (China). Dept. of Applied Physics

    2016-11-01

    The spin Hamiltonian parameters and local structures are theoretically studied for Cu{sup 2+}-doped alkaline earth lead zinc phosphate (RPPZ, R=Mg, Ca, Sr, and Ba) glasses based on the high-order perturbation calculations for a tetragonally elongated octahedral 3d{sup 9} cluster. The relative elongation ratios are found to be ρ ∼ 3.2%, 4.4%, 4.6%, and 3.3% for R=Mg, Ca, Sr, and Ba, respectively, because of the Jahn-Teller effect. The whole decreasing crystal-field strength Dq and orbital reduction factor k from Mg to Sr are ascribed to the weakening electrostatic coulombic interactions and the increasing probability of productivity of nonbridge oxygen (and hence increasing Cu{sup 2+}-O{sup 2-} electron cloud admixtures) under PbO addition, respectively, with increasing alkali earth ionic radius. The anomalies (the largest Dq and the next highest k among the systems) for R=Ba are attributed to the cross linkage of this large cation in the network. The overall increasing order (Mg≤Baglasses containing copper dopants.

  1. Spin-Glass-Like Behavior and Topological Hall Effect in SrRuO3/SrIrO3 Superlattices for Oxide Spintronics Applications.

    Science.gov (United States)

    Pang, Bin; Zhang, Lunyong; Chen, Y B; Zhou, Jian; Yao, Shuhua; Zhang, Shantao; Chen, Yanfeng

    2017-01-25

    The heterostructure interface provides a powerful platform for exploring rich emergent phenomena, such as interfacial superconductivity and nontrivial topological surface states. Here, SrRuO3/SrIrO3 superlattices were epitaxially synthesized. The magnetic and magneto-transport properties of these superlattices were characterized. A broad cusp-type splitting in the zero-field-cooling/field-cooling temperature-dependent magnetization and magnetization relaxation, which follows the modified stretched function model, accompanied by double hysteresis magnetization loops were demonstrated. These physical effects were modulated by the SrIrO3 layer thickness, which confirms the coexistence of interfacial spin glass and ferromagnetic ordering in the superlattices. In addition, the topological Hall effect was observed at low temperatures, and it is weakened with the increase of the SrIrO3 layer thickness. These results suggest that a noncoplanar spin texture is generated at the SrRuO3/SrIrO3 interfaces because of the interfacial Dzyaloshinskii-Moriya interaction. This work demonstrates that SrIrO3 can effectively induce interfacial Dzyaloshinskii-Moriya interactions in superlattices, which would serve as a mechanism to develop spintronic devices with perovskite oxides.

  2. Magneto-thermally activated spin-state transition in La0.95Ca0.05CoO3: magnetically-tunable dipolar glass and giant magneto-electricity.

    Science.gov (United States)

    Pandey, Suchita; Kumar, Jitender; Awasthi, A M

    2016-03-01

    The magneto-dielectric spectroscopy of La0.95Ca0.05CoO3 covering the crossover of spin states reveals the strong coupling of its spin and dipolar degrees of freedom. The signature of the spin-state transition at 30 K clearly manifests in the magnetization data at a 1 Tesla optimal field. Our Co L3,2-edge X-ray absorption spectrum on the doped specimen is consistent with its suppressed low-to-intermediate spin-state transition temperature at ∼30 K compared to ∼150 K, documented for pure LaCoO3. The dispersive activation step in the dielectric constant with the associated relaxation peak in imaginary permittivity characterize the allied influence of coexistent spin-states on the dielectric character. Dipolar relaxation in the low-spin regime below the transition temperature is partly segmental (Vogel-Fulcher-Tamman (VFT) kinetics) and features magnetic-field tunability, whereas in the low/intermediate-spin disordered state above ∼30 K, it is uncorrelated (Arrhenic kinetics) and almost impervious to the magnetic field H. Kinetics-switchover defines the dipolar-glass transition temperature Tg(H) (=27 K|0T), below which their magneto-thermally-activated cooperative relaxations freeze out by the VFT temperature T0(H) (=15 K|0T). An applied magnetic field facilitates thermal activation in toggling the low spins up into the intermediate states. Consequently, the downsized dipolar-glass segments in the low-spin state and the independent dipoles in the intermediate state exhibit accelerated dynamics. A critical 5 Tesla field collapses the entire relaxation kinetics into a single Arrhenic behaviour, signaling that the dipolar glass is completely devitrified under all higher fields. The magneto-electricity (ME) spanning sizeable thermo-spectral range registers diverse signatures here in kinetic, spectral, and field behaviors, in contrast to the static/perturbative ME observed close to the spin-ordering in typical multiferroics. Intrinsic magneto-dielectricity (50%) along

  3. Optical absorption and electron spin resonance studies of Cu2+ in Li2O–Na2O–B2O3–As2O3 glasses

    Indian Academy of Sciences (India)

    N Srinivasa Rao; Shashidhar Bale; M Purnima; K Siva Kumar; Syed Rahman

    2005-10-01

    The local structure around Cu2+ ion has been examined by means of electron spin resonance and optical absorption measurements in Li2O–(40 – )Na2O–50B2O3–10As2O3 glasses. The site symmetry around Cu2+ ions is tetragonally distorted octahedral. The ground state of Cu2+ is $d_{x^2–y^2}$. The glass exhibited broad absorption band near infrared region and small absorption band around 548 nm, which was assigned to the ${}^{2}B_{1g} \\rightarrow {}^{2}E_{g}$ transition.

  4. Investigation of magnetic spin glass property in La{sub 0.5}Bi{sub 0.5}MnO{sub 3} sample using non-linear AC susceptibility measurements

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Punith V., E-mail: drvldayal@gmail.com; Manju, M. R., E-mail: drvldayal@gmail.com; Dayal, Vijaylakshmi, E-mail: drvldayal@gmail.com [Department of Physics, Maharaja Institute of Technology, Mysore-571438, Karnataka (India)

    2014-04-24

    We present a comprehensive study on origin of Spin Glass (SG) property in polycrystalline La{sub 0.5}Bi{sub 0.5}MnO{sub 3} perovskite oxide using linear and higher order ac susceptibility (χ) measurements. The third order harmonic susceptibility (χ{sub 3}) vs. temperature (K) with varying magnetic fields from 0.95 to 9.45 Oe and the divergence in their χ{sub 3} (max) allows us to infer the SG behavior occurring in the sample possibly due to co-operative freezing of the spins.

  5. Room temperature relaxor ferroelectricity and spin glass behavior in Sr{sub 2}FeTiO{sub 6} double perovskite

    Energy Technology Data Exchange (ETDEWEB)

    Neenu Lekshmi, P.; Savitha Pillai, S. [Materials Science and Technology Division, National Institute for Interdisciplinary Science and Technology NIIST, CSIR, Trivandrum 695 019 (India); Suresh, K.G. [Department of Physics, Indian Institute of Technology Bombay, Mumbai 400 076 (India); Santhosh, P.N. [Department of Physics, Indian Institute of Technology Madras, Chennai 600 036 (India); Varma, Manoj Raama, E-mail: manojraamavarma@yahoo.co.uk [Materials Science and Technology Division, National Institute for Interdisciplinary Science and Technology NIIST, CSIR, Trivandrum 695 019 (India)

    2012-05-05

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

  6. On the mutual relationships between spin probe mobility, free volume and relaxation dynamics in organic glass-formers: Glycerol

    Science.gov (United States)

    Bartoš, J.; Švajdlenková, H.

    2017-02-01

    The rotation dynamics of the spin probe TEMPO in glycerol from ESR is compared with the ortho-positronium (o-Ps) annihilation from PALS and interpreted using the relaxation dynamics from BDS. Rotation time scale within the slow motion regime exhibits two Arrhenius regions with the characteristic ESR temperature, TX1τ, close to the characteristic PALS temperature, Tb1L, which is related to the secondary β process above Tg. Next, a slow to fast motion regime transition at the characteristic ESR temperature, Tcτ, close to the characteristic PALS temperature, Tb2L, followed by non-Arrhenius fast motion regime region is fully coupled with the primary α process.

  7. Bridging amount of spin-glasses over ferromagnetic/antiferromagnetic thin films and bit-cell dispersion of exchange bias in corresponding TA-MRAM devices

    Science.gov (United States)

    Akmaldinov, Kamil; Ducruet, Clarisse; Alvarez-Herault, Jeremy; Baltz, Vincent

    2015-03-01

    For thermally-assisted magnetic random access memories (TA-MRAM), lowering bit-cells dispersions of exchange bias is necessary. In this study, we prove that spin-glass-like phases (SG) spread over the ferromagnetic/antiferromagnetic (F/AF) storage layer are the main cause of such distributions once the film is nanofabricated into a device. In particular, we show that the less the SG, the lower the bit-cell dispersion. More precisely, the amount of SG was varied from sample to sample by sputtering various AFs: IrMn, FeMn and their alloys. Blocking temperature distributions were measured to quantify the amount of SG at the wafer level. The wafers were then patterned to obtain 1kb devices and all the cells were tested electrically. Finally, the resulting loop shift cumulative distribution functions accounting for the bit-cell dispersions were correlated to the initial amount of SG. In addition to bridging the gap between fundamental SG and a technological application, we also demonstrated that blocking temperature distributions are a versatile method to qualify TA-MRAM production batches before processing. Univ. Grenoble-Alpes/CNRS/INAC-CEA, 38000 Grenoble, France.

  8. Spin-glass-like behavior and negative thermal expansion in antiperovskite Mn{sub 3}Ni{sub 1−x}Cu{sub x}N compounds

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Lei [Center for Condensed Matter and Materials Physics, Department of Physics, Beihang University, 100191 Beijing (China); Univ. Grenoble Alpes, Inst NEEL, F-38000 Grenoble (France); CNRS, Inst NEEL, F-38000 Grenoble (France); Wang, Cong, E-mail: congwang@buaa.edu.cn; Sun, Ying [Center for Condensed Matter and Materials Physics, Department of Physics, Beihang University, 100191 Beijing (China); Colin, Claire V. [Univ. Grenoble Alpes, Inst NEEL, F-38000 Grenoble (France); CNRS, Inst NEEL, F-38000 Grenoble (France); Chu, Lihua [State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, School of Renewable Energy, North China Electric Power University, Beijing 102206 (China)

    2015-06-07

    The Cu-doping effect on the lattice and magnetic properties in Mn{sub 3}Ni{sub 1−x}Cu{sub x}N (x = 0, 0.3, 0.5, 0.7, 1.0) was extensively investigated. We observed that the Cu-doping at the Ni site complicated the magnetic ground states, which induced the competition of antiferromagnetic and ferromagnetic interactions. Spin-glass-like behavior, arising from possible site-randomness and competing interactions of magnetism, was observed in compounds with x = 0.3, 0.5, and 0.7, and typically discussed by means of the measurement of ac magnetic susceptibility for x = 0.7. The negative thermal expansion (NTE) behavior, due to the magnetic ordering transition, was observed in Mn{sub 3}Ni{sub 1−x}Cu{sub x}N compounds using variable temperature x-ray diffraction. It reveals that the introduction of Cu effectively broadens the temperature range displaying negative thermal expansion. The relationship between the local lattice distortion and the competing magnetic ground states might play an important role in broadening the NTE temperature range in this antiperovskite compound.

  9. Spin glass and ferromagnetic properties of Ce(Cu{sub 1-x}Ni{sub x}){sub 4}Mn alloys: Multicritical points in the magnetic phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Synoradzki, K., E-mail: karol.synoradzki@ifmpan.poznan.pl; Toliński, T.

    2016-07-01

    We report on the CeNi{sub 4}Mn (ferromagnet FM) - CeCu{sub 4}Mn (spin-glass SG) transformation leading to a complex magnetic phase diagram (MPD). It is verified that all the Ce(Cu{sub 1-x}Ni{sub x}){sub 4}Mn alloys are isostructural and the transformation is governed only by the Cu-Ni substitution. MPD is built based on the magnetic dc/ac susceptibility measurements and reveals SG formation as well as the region of the coexistence of the FM and SG state in the middle range of the Ni concentration. The complex MPD is explained by clusters formation and a competition of interactions between various crystallographic sites of the hexagonal CaCu{sub 5}-type structure, mainly the 3g-3g and 3g-2c interactions. The predominance of the SG state is confirmed by the analysis of the frequency dependence of the ac magnetic susceptibility components and the relaxation of the remanent magnetization. Additionally, the presence of two multicritical points is observed. - Highlights: • We fully characterized the magnetic properties of Ce(Cu{sub 1-x}Ni{sub x}){sub 4}Mn alloys. • We show the presence of complex magnetic behaviour due to atomic-site disorder. • Magnetic phase diagram revels mixed-phase ground state. • Two multicritical points on magnetic phase diagram occurs.

  10. Enhancement of the electrical characteristics of MOS capacitors by reducing the organic content of H{sub 2}O-diluted Spin-On-Glass based oxides

    Energy Technology Data Exchange (ETDEWEB)

    Molina, Joel, E-mail: jmolina@inaoep.mx [National Institute of Astrophysics, Optics and Electronics, Electronics Department, Luis Enrique Erro 1, PO BOX 51 and 216, Tonantzintla, Puebla 72000 (Mexico); Munoz, Ana; Torres, Alfonso; Landa, Mauro; Alarcon, Pablo; Escobar, Manuel [National Institute of Astrophysics, Optics and Electronics, Electronics Department, Luis Enrique Erro 1, PO BOX 51 and 216, Tonantzintla, Puebla 72000 (Mexico)

    2011-10-25

    In this work, the physical, chemical and electrical properties of Metal-Oxide-Semiconductor (MOS) capacitors with Spin-On-Glass (SOG)-based thin films as gate dielectric have been investigated. Experiments of SOG diluted with two different solvents (2-propanol and deionized water) were done in order to reduce the viscosity of the SOG solution so that thinner films (down to {approx}20 nm) could be obtained and their general characteristics compared. Thin films of SOG were deposited on silicon by the sol-gel technique and they were thermally annealed using conventional oxidation furnace and Rapid Thermal Processing (RTP) systems within N{sub 2} ambient after deposition. SOG dilution using non-organic solvents like deionized water and further annealing (at relatively high temperatures {>=}450 deg. C) are important processes intended to reduce the organic content of the films. Fourier-Transform Infrared (FTIR) Spectroscopy results have shown that water-diluted SOG films have a significant reduction in their organic content after increasing annealing temperature and/or dilution percentage when compared to those of undiluted SOG films. Both current-voltage (I-V) and capacitance-voltage (C-V) measurements show better electrical characteristics for SOG-films diluted in deionized water compared to those diluted in 2-propanol (which is an organic solvent). The electrical characteristics of H{sub 2}O-diluted SOG thin films are very similar to those obtained from high quality thermal oxides so that their application as gate dielectrics in MOS devices is promising. Finally, it has been demonstrated that by reducing the organic content of SOG-based thin films, it is possible to obtain MOS devices with better electrical properties.

  11. Magnetic nature of the austenite-martensite phase transition and spin glass behaviour in nanostructured Mn2Ni1.6Sn0.4 melt-spun ribbons

    Science.gov (United States)

    Singh, Nidhi; Borgohain, Barsha; Srivastava, A. K.; Dhar, Ajay; Singh, H. K.

    2016-03-01

    Nanocrystalline ribbons of inverse Heusler alloy Mn2Ni1.6Sn0.4 have been synthesised by melt spinning of the arc-melted bulk precursor. The single-phase ribbons crystallize into a cubic structure and exhibit very fine crystallite size of phase transition that begins at M S ≈ 249 K and finishes at M f ≈ 224 K. During warming, the reverse AFM-M to FM-A transitions begins at A s ≈ 240 K and finishes at A f ≈ 261 K. A re-entrant FM transition is observed in the M-phase at T_{{CM}} ≈ 145 K. These transitions are also confirmed by temperature-dependent resistivity ( ρ- T) measurements. The hysteretic behaviour of M- T and ρ- T in the temperature regime spanned by the A-M transition is a manifestation of the first-order phase transition. M- T and ρ- T data also provide unambiguous evidence in favour of spin glass at T AC susceptibility measurements, confirms the existence of canonical spin glass at T phase.

  12. Optimization of Pr(0.9)Ca(0.1)MnO(3) thin films and observation of coexisting spin-glass and ferromagnetic phases at low temperature.

    Science.gov (United States)

    Svedberg, M; Majumdar, S; Huhtinen, H; Paturi, P; Granroth, S

    2011-09-28

    Optimization of thin films of small bandwidth manganite, Pr(1-x)Ca(x)MnO3 (for x = 0.1), and their magnetic properties are investigated. Using different pulsed laser deposition (PLD) conditions, several films were deposited from the stoichiometric target material on SrTiO3 (001) substrate and their thorough structural and magnetic characterizations were carried out using x-ray diffraction, atomic force microscopy, x-ray photoelectron spectroscopy (XPS), SQUID magnetometry and ac susceptibility measurements. A systematic investigation shows that irrespective of the growth temperature (between 550 and 750 °C), all the as-deposited films have twin boundaries and magnetic double phases. Post-annealing in partial or full oxygen pressure removes the extra phase and the twin boundaries. Zero-field-cooled magnetization data show an antiferromagnetic to paramagnetic transition at around 100 K whereas the field-cooled magnetization data exhibit a paramagnetic to ferromagnetic transition close to 120 K. However, depending on the oxygen treatments, the saturation magnetization and Curie temperature of the films change significantly. Redistribution of oxygen vacancies due to annealing treatments leading to a change in ratio of Mn3+ and Mn4+ in the films is observed from XPS measurements. Low temperature (below 100 K) dc magnetization of these films shows metamagnetic transition, high coercivity and irreversibility magnetizations, indicating the presence of a spin-glass phase at low temperature. The frequency dependent shift in spin-glass freezing temperature from ac susceptibility measurement confirms the coexistence of spin-glass and ferromagnetic phases in these samples at low temperature.

  13. Muon-spin rotation measurements of an unusual vortex-glass phase in the layered superconductor Bi2.15Sr1.85CaCu2O8+δ.

    Science.gov (United States)

    Heron, D O G; Ray, S J; Lister, S J; Aegerter, C M; Keller, H; Kes, P H; Menon, G I; Lee, S L

    2013-03-08

    Muon-spin rotation measurements, performed on the mixed state of the classic anisotropic superconductor Bi(2.15)Sr(1.85)CaCu(2)O(8+δ), obtain quantities directly related to two- and three-body correlations of vortices in space. A novel phase diagram emerges from such local probe measurements of the bulk, revealing an unusual glassy state at intermediate fields which appears to freeze continuously from the equilibrium vortex liquid but differs both from the lattice and the conventional high-field vortex glass state in its structure.

  14. Evidence of spin-glass like ordering and exchange bias effect in antisite-disordered nanometric La1.5Ca0.5CoMnO6 double perovskite

    Science.gov (United States)

    Sahoo, R. C.; Paladhi, D.; Nath, T. K.

    2017-08-01

    Single-phase polycrystalline La1.5Ca0.5CoMnO6 double perovskite nanoparticles (∼25 nm) have been synthesized by chemical sol-gel method. We report here the structural, magnetic and transport properties using X-ray diffraction, dc magnetization, ac susceptibility, exchange bias and dc resistivity measurements. The Rietveld refinement of X-ray diffraction pattern reveals that the La1.5Ca0.5CoMnO6 (LCCMO) system crystallizes in orthorhombic structure with pbnm space group. Mn and Co ions are not completely ordered on the B sites due to the presence of about 30% antisite-disorder in the system. The ordering of Co2+ and Mn4+ gives rise to the ferromagnetism below 145 K. A spin glass like ground state has also been observed near 37.6(4) K, arising mainly due to the presence of competing magnetic interactions and antisite-disorder in the LCCMO nanoparticles. The frequency dependence peak shift of the Ac-susceptibility peak in the glassy state follows the critical slowing down model. The observed memory effect in ac susceptibility data reveals the existence of interacting clusters in a competing magnetic interactions state. The presence of noticeable exchange bias effect can be best explained on the basis of uncompensated interface (ferromagnetic/spin-glass) spins of antisite-disordered LCCMO system. This anti-site disordered nanocompound exhibits semiconducting behavior with variable range hopping kind of electronic conduction mechanism in the temperature range of 200-300 K. We have also observed large negative magnetoresistance (-30% at 100 K and 60 kOe) mainly due to the spin-polarized transport across the grain boundaries.

  15. Observation of the second-order magnetic and reentrant spin-glass transitions in LiNi{sub 0.5}Mn{sub 0.5}O{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Bie, Xiaofei; Gao, Yu; Yang, Xu; Wei, Yingjin [Key Laboratory of Advanced Batteries Physics and Technology (Ministry of Education), College of Physics, Jilin University, Changchun 130012 (China); Ehrenberg, Helmut; Hinterstein, Manuel [Institute for Applied Materials (IAM), Karlsruhe Institute of Technology (KIT), D-76344 Eggenstein-Leopoldshafen (Germany); Chen, Gang; Wang, Chunzhong [Key Laboratory of Advanced Batteries Physics and Technology (Ministry of Education), College of Physics, Jilin University, Changchun 130012 (China); Du, Fei, E-mail: dufei@jlu.edu.cn [Key Laboratory of Advanced Batteries Physics and Technology (Ministry of Education), College of Physics, Jilin University, Changchun 130012 (China)

    2015-03-25

    Highlights: • Rietveld refinement confirms that the sample is a single phase with the rhombohedral layered structure. • Dc susceptibility data suggest a FiM transition at 108 K. • The results of Arrott method indication of the second-order character of the transition. • The ac susceptibility data confirm the SG transition in LiNi{sub 0.5}Mn{sub 0.5}O{sub 2} at 14 K. - Abstract: The structure and magnetic properties of LiNi{sub 0.5}Mn{sub 0.5}O{sub 2} were studied by synchrotron X-ray diffraction, dc and ac susceptibilities. The material showed a continuous magnetic transition from paramagnetism into ferrimagnetism, followed by a spin glass with the decrease of temperature. Using a criterion given by Banerjee to distinguish first-order magnetic transition from second-order ones, it is shown that the ferrimagnetic transition at 108 K belongs to the second-order type. The frequency dependence of peak intensity and the shift in ac susceptibility at 14 K suggest a reentrant spin glass transition in LiNi{sub 0.5}Mn{sub 0.5}O{sub 2}.

  16. Order and disorder in the local and long-range structure of the spin-glass pyrochlore, Tb{sub 2}Mo{sub 2}O{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Yu; Huq, Ashfia; Booth, Corwin H.; Ehlers, Georg; Greedan, John E.; Gardner, Jason S.

    2011-02-11

    To understand the origin of the spin-glass state in molybdate pyrochlores, the structure of Tb{sub 2}Mo{sub 2}O{sub 7} is investigated using two techniques: the long-range lattice structure was measured using neutron powder diffraction (NPD), and local structure information was obtained from the extended x-ray absorption fine structure (EXAFS) technique. While the long-range structure appears generally well ordered, enhanced mean-squared site displacements on the O(1) site and the lack of temperature dependence of the strongly anisotropic displacement parameters for both the Mo and O(1) sites indicate some disorder exists. Likewise, the local structure measurements indicate some Mo-Mo and Tb-O(1) nearest-neighbor disorder exists, similar to that found in the related spin-glass pyrochlore, Y{sub 2}Mo{sub 2}O{sub 7}. Although the freezing temperature in Tb{sub 2}Mo{sub 2}O{sub 7}, 25 K, is slightly higher than in Y{sub 2}Mo{sub 2}O{sub 7}, 22 K, the degree of local pair distance disorder is actually less in Tb{sub 2}Mo{sub 2}O{sub 7}. This apparent contradiction is considered in light of the interactions involved in the freezing process.

  17. Spectroscopic and Physical Properties of Mn2+ spin probe in ROP2O5-ZnO-Pb3O4 (R=Li, Na and K Glasses

    Directory of Open Access Journals (Sweden)

    S. Sreehari Sastry

    2015-04-01

    Full Text Available RO-P2O5-ZnO-Pb3O4 (R=Li, Na and K glasses containing 0.1concentrations of MnO have been prepared. The structural, optical and physical properties of prepared glasses are studied by XRD, UV-Visible, EPR and FTIR techniques. The nature of local symmetry and structural information of the neighboring atoms of dopant ions (Mn2+ in the host matrix have been understood by evaluating the crystal field strength (Dq and Racah (B & C parameters. The combined analysis of optical absorption and EPR spectroscopy has indicated that the manganese ions exist in Mn2+ (in octahedral local coordination sites. FTIR results showed that PO4 are the main structural unit of the glass system and the manganese ions are located in the glass matrix network.

  18. Simulation of Glass Fiber Forming Processes

    DEFF Research Database (Denmark)

    Von der Ohe, Renate

    Two glass fiber forming processes have been simulated using FEM, which are the drawing of continuous glass fibers for reinforcement purposes and the spinning of discontinuous glass fibers - stone wool for insulation. The aim of this work was to set up a numerical model for each process, and to use...

  19. Interfacial analysis and properties of regioregular Poly (3-Hexyl thiophene) spin-coated on an Indium tin oxide coated glass substrate

    CSIR Research Space (South Africa)

    Malgas, GF

    2008-08-01

    Full Text Available Interfacial analysis of the rrP3HT samples spincoated on a glass substrate was studied in detail using transmission electron microscopy (TEM) and SEM measurements. Very homogeneous and smooth polymer (P3HT and PEDOT:PSS) layers are observed...

  20. Frustrated spin systems

    CERN Document Server

    2013-01-01

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

  1. Double spin-glass-like behavior and antiferromagnetic superexchange interaction between Fe3+ ions in α-Ga2-xFexO3 (0 ≤ x ≤ 0.4)

    Science.gov (United States)

    Lv, Yi-Fei; Xiang, Jian-Yong; Wen, Fu-Sheng; Lv, Wei-Ming; Hu, Wen-Tao; Liu, Zhong-Yuan

    2015-03-01

    Single phase of Fe3+-doped α-Ga2-xFexO3 (α-GFxO, x = 0.1, 0.2, 0.3, 0.4) is synthesized by treating the β-Ga2-xFexO3 (β-GFxO) precursors at high temperatures and high pressures. Rietveld refinements of the X-ray diffraction data show that the lattice constants increase monotonically with the increase of Fe3+ content. Calorimetric measurements show that the temperature of the phase transition from α-GFxO to β-GFxO increases, while the associated enthalpy change decreases upon increasing Fe3+ content. The optical energy gap deduced from the reflectance measurement is found to decrease monotonically with the increase in Fe3+ content. From the measurements of magnetic field-dependent magnetization and temperature-dependent inverse molar susceptibility, we find that the superexchange interaction between Fe3+ ions is antiferromagnetic. Remnant magnetization is observed in the Fe3+-doped α-GFxO and is attributed to the spin glass in the magnetic sublattice. At high Fe3+ doping level (x = 0.4), two evident peaks are observed in the image part of the AC susceptibility . The frequency dependence in intensity of these two peaks as well as two spin freezing temperatures observed in the DC magnetization measurements of α-GF0.4O is suggested to be the behavior of two spin glasses. Project supported by the National Basic Research Program of China (Grant No. 2010CB731605), the National Science Fund for Distinguished Young Scholars of China (Grant No. 51025103), the National Natural Science Foundation of China (Grant Nos. 51172198 and 51102206), the Natural Science Foundation of Hebei Province, China (Grant No. E2014203144), the Science Foundation for the Excellent Youth Scholars from Universities and Colleges of Hebei Province, China (Grant No. YQ2014009), and the Research Program of the College Science & Technology of Hebei Province, China (Grant No. QN2014047).

  2. Glass sealing

    Energy Technology Data Exchange (ETDEWEB)

    Brow, R.K.; Kovacic, L.; Chambers, R.S. [Sandia National Labs., Albuquerque, NM (United States)

    1996-04-01

    Hernetic glass sealing technologies developed for weapons component applications can be utilized for the design and manufacture of fuel cells. Design and processing of of a seal are optimized through an integrated approach based on glass composition research, finite element analysis, and sealing process definition. Glass sealing procedures are selected to accommodate the limits imposed by glass composition and predicted calculations.

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

    OpenAIRE

    Mojtaba Nasr-Esfahani; Mohammad Hossein Habibi

    2008-01-01

    New composite films (P25SGF-MC-Ag, MPC500SGF-MC-Ag, and ANPSGF-MC-Ag) have been synthesized by a modified sol-gel method using different particle sizes of TiO2 powder and silver addition. Nanostructure TiO2/Ag composite thin films were prepared by a sol-gel spin and dip coating technique. while, by introducing methyl cellulose (MC) porous, TiO2/Ag films were obtained after calcining at a temperature of 500°C. The as-prepared TiO2 and TiO2/Ag films were characterized by X-ray diffractometry, a...

  4. Spin foams without spins

    Science.gov (United States)

    Hnybida, Jeff

    2016-10-01

    We formulate the spin foam representation of discrete SU(2) gauge theory as a product of vertex amplitudes each of which is the spin network generating function of the boundary graph dual to the vertex. In doing so the sums over spins have been carried out. The boundary data of each n-valent node is explicitly reduced with respect to the local gauge invariance and has a manifest geometrical interpretation as a framed polyhedron of fixed total area. Ultimately, sums over spins are traded for contour integrals over simple poles and recoupling theory is avoided using generating functions.

  5. Exploring frustrated magnetism with artificial spin ice

    Science.gov (United States)

    Gilbert, Ian; Ilic, B. Robert

    2016-10-01

    Nanomagnet arrays known as artificial spin ice provide insight into the microscopic details of frustrated magnetism because, unlike natural frustrated magnets, the individual moments can be experimentally resolved and the lattice geometry can be easily tuned. Most studies of artificial spin ice focus on two lattice geometries, the square and the kagome lattices, due to their direct correspondence to natural spin ice materials such as Dy2Ti2O7. In this work, we review experiments on these more unusual lattice geometries and introduce a new type of nanomagnet array, artificial spin glass. Artificial spin glass is a two-dimensional array of nanomagnets with random locations and orientations and is designed to elucidate the more complex frustration found in spin glass materials.

  6. Magnetic structures of (Co{sub 2-x}Ni{sub x})(OH)PO{sub 4} (x = 0.1,0.3) spin glass-like state in antiferromagnetically ordered phases

    Energy Technology Data Exchange (ETDEWEB)

    Pedro, I de [Departamento de QuImica Inorganica, Facultad de Ciencia y TecnologIa, Universidad del PaIs Vasco, 48080 Bilbao (Spain); Rojo, J M [Departamento de QuImica Inorganica, Facultad de Ciencia y TecnologIa, Universidad del PaIs Vasco, 48080 Bilbao (Spain); Pizarro, J L [Departamento de MineralogIa y PetrologIa, Facultad de Ciencia y TecnologIa, Universidad del PaIs Vasco, 48080 Bilbao (Spain); Fernandez, J RodrIguez [CITIMAC, Facultad de Ciencias, Universidad de Cantabria, 39005 Santander (Spain); Marcos, J Sanchez [CITIMAC, Facultad de Ciencias, Universidad de Cantabria, 39005 Santander (Spain); Fernandez-DIaz, M T [Institut Laue-Langevin, BP 156X, F-38042 Grenoble Cedex (France); Arriortua, M I [Departamento de MineralogIa y PetrologIa, Facultad de Ciencia y TecnologIa, Universidad del PaIs Vasco, 48080 Bilbao (Spain); Rojo, T [Departamento de QuImica Inorganica, Facultad de Ciencia y TecnologIa, Universidad del PaIs Vasco, 48080 Bilbao (Spain)

    2006-04-19

    Compounds of the general formula Co{sub 2-x}Ni{sub x}(OH)PO{sub 4} (x = 0.1, 0.3) have been synthesized under mild hydrothermal conditions. Neutron powder diffraction, susceptibility and heat capacity measurements were carried out on polycrystalline samples. The cobalt-nickel compounds are ordered as three-dimensional antiferromagnets with ordering temperatures of 70 and 64 K for x = 0.1 and x = 0.3, respectively. The magnetic study shows a spin glass-like state below 11 and 5 K for Co{sub 1.9}Ni{sub 0.1}(OH)PO{sub 4} and Co{sub 1.7}Ni{sub 0.3}(OH)PO{sub 4}, respectively. Specific heat data present peaks at 68 and 61 K for Co{sub 1.9}Ni{sub 0.1} and Co{sub 1.7}Ni{sub 0.3}, respectively. These peaks show broad shoulders between approximately 15 and 40 K. The lack of any distinguishable anomaly below 10 K supports the spin glass nature of the low temperature transitions. Refinement of room temperature neutron diffraction data indicates that the Ni(II) ions are in octahedral co-ordination with the practical absence of these ions in the trigonal bipyramidal sites. The magnetic structures of Co{sub 2-x}Ni{sub x}(OH)PO{sub 4} consist of ferromagnetic arrangements between the octahedral chains and trigonal bipyramidal dimers within the xz plane with the magnetic moments along the z axis. The ferromagnetic layers are disposed antiparallel to one another along the y direction establishing the three-dimensional antiferromagnetic order (T{sub N}{approx}70 K for Co{sub 1.9}Ni{sub 0.1} and {approx}64 K for Co{sub 1.7}Ni{sub 0.3}). The different exchange pathways, the anisotropy of the Co(II) ions and the frustration of the magnetic moments in the trigonal bipyramidal geometry could be responsible for the freezing process.

  7. Knot spinning

    OpenAIRE

    Friedman, Greg

    2004-01-01

    This is an introduction to the construction of higher-dimensional knots by spinning methods. Simple spinning of classical knots was introduced by E. Artin in 1926, and several generalizations have followed. These include twist spinning, superspinning or p-spinning, frame spinning, roll spinning, and deform spinning. We survey these constructions and some of their most important applications, as well as some newer hybrids due to the author. The exposition, meant to be accessible to a broad aud...

  8. Bose-Einstein condensation in quantum glasses

    OpenAIRE

    2009-01-01

    The role of geometrical frustration in strongly interacting bosonic systems is studied with a combined numerical and analytical approach. We demonstrate the existence of a novel quantum phase featuring both Bose-Einstein condensation and spin-glass behaviour. The differences between such a phase and the otherwise insulating "Bose glasses" are elucidated.

  9. Spin glass state and its correlations with the magnetic and electrical properties as well as with the defectiveness in the spinels CuCr{sub 2}X{sub 4} (X = S, Se) doped with Sb

    Energy Technology Data Exchange (ETDEWEB)

    Krok-Kowalski, J. [University of Silesia, Institute of Physics, ul. Uniwersytecka 4, 40007 Katowice (Poland)]. E-mail: warcz@us.edu.pl; Warczewski, J. [University of Silesia, Institute of Physics, ul. Uniwersytecka 4, 40007 Katowice (Poland); Krajewski, K. [University of Silesia, Institute of Physics, ul. Uniwersytecka 4, 40007 Katowice (Poland); Duda, H. [University of Silesia, Institute of Physics, ul. Uniwersytecka 4, 40007 Katowice (Poland); Gusin, P. [University of Silesia, Institute of Physics, ul. Uniwersytecka 4, 40007 Katowice (Poland); Sliwinska, T. [University of Silesia, Institute of Physics, ul. Uniwersytecka 4, 40007 Katowice (Poland); Pacyna, A. [Institute of Nuclear Physics, ul. Radzikowskiego 152, 31342 Krakow (Poland); Mydlarz, T. [International Laboratory of High Magnetic Fields and Low Temperatures, ul. Gajowicka 95, 53529 Wroclaw (Poland); Matyjasik, S. [International Laboratory of High Magnetic Fields and Low Temperatures, ul. Gajowicka 95, 53529 Wroclaw (Poland); Malicka, E. [University of Silesia, Institute of Chemistry, ul. Szkolna 9, 40006 Katowice (Poland); Kita, A. [University of Silesia, Institute of Chemistry, ul. Szkolna 9, 40006 Katowice (Poland)

    2007-03-14

    High degree of defectiveness both in the stoichiometric CuCr{sub 2-x}Sb {sub x}S{sub 4} (x = 0.3, 0.4, 0.5) and nonstoichiometric Cu{sub 1+x}Cr{sub 1.5+y}Sb{sub 0.5+z}Se{sub 4+t} (where: -0.02 {<=} x {<=} 0.01, 0.03 {<=} y {<=} 0.35, -0.2 {<=} z {<=} -0.02, 0.01 {<=} t {<=} 0.08) spinels doped with Sb has been determined with the aid of the vacancy model. From the analysis carried out of the effective magnetic moments and the exchange integrals, it follows that in the spinels with sulphur mainly the cation subarrays are defected whereas in the spinels with selenium the defectiveness appears mainly in the anion subarrays. It turned out that in the spinels with sulphur the ferromagnetic cluster spin glass states appear accompanied by the large negative magnetoresistance, whereas in the spinels with selenium the corresponding clusters are antiferromagnetic and the giant magnetoresistance has been observed both positive and negative. A jump-like phase transition was here observed changing both the sign and the measured value of the magnetoresistance from -4433% at 153.2 K up to +980% at 154.24 K. Moreover, in the spinels with selenium both semiconductor-metal and metal-semiconductor phase transitions have been observed from the temperature dependence of the resistance.

  10. Bose glass behavior in (Yb1 -xLux)4As3 representing randomly diluted quantum spin-1/2 chains

    Science.gov (United States)

    Kamieniarz, G.; Matysiak, R.; Gegenwart, P.; Ochiai, A.; Steglich, F.

    2016-09-01

    The site-diluted compound (Yb1-xLux) 4As3 is a scarce realization of the linear Heisenberg antiferromagnet partitioned into finite-size segments and is an ideal model compound for studying field-dependent effects of quenched disorder in the one-dimensional antiferromagnets. It differentiates from the systems studied so far in two aspects—the type of randomness and the nature of the energy gap in the pure sample. We have measured the specific heat of single-crystal (Yb1-xLux) 4As3 in magnetic fields up to 19.5 T. The contribution C⊥ arising from the magnetic subsystem in an applied magnetic field perpendicular to the chains is determined. Compared to pure Yb4As3 , for which C⊥ indicates a gap opening, for diluted systems a nonexponential decay is found at low temperatures which is consistent with the thermodynamic scaling of the specific heat established for a Bose-glass phase.

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

    Directory of Open Access Journals (Sweden)

    Mojtaba Nasr-Esfahani

    2008-01-01

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

  12. Spin Foams Without Spins

    CERN Document Server

    Hnybida, Jeff

    2015-01-01

    We formulate the spin foam representation of discrete SU(2) gauge theory as a product of vertex amplitudes each of which is the spin network generating function of the boundary graph dual to the vertex. Thus the sums over spins have been carried out. We focus on the character expansion of Yang-Mills theory which is an approximate heat kernel regularization of BF theory. The boundary data of each $n$-valent node is an element of the Grassmannian Gr(2,$n$) which carries a coherent representation of U($n$) and a geometrical interpretation as a framed polyhedron of fixed total area. Ultimately, sums over spins are traded for contour integrals over simple poles and recoupling theory is avoided using generating functions.

  13. Anisotropic thermal expansion behavior of thin films of polymethylsilsesquioxane, a spin-on-glass dielectric for high-performance integrated circuits.

    Science.gov (United States)

    Oh, Weontae; Ree, Moonhor

    2004-08-03

    Thin films of poly(methylsilsesquioxane) (PMSSQ) are candidates for use as interdielectric layers in advanced semiconductor devices with multilayer structures. We prepared thin films of PMSSQ with thicknesses in the range 25.0-1151.0 nm by spin-casting its soluble precursor onto Si and GaAs substrates with native oxide layers and then drying and curing the films under a nitrogen atmosphere at temperatures in the range 250-400 degrees C. The out-of-plane thermal expansion coefficient alpha(perpendicular) of each film was measured over the temperature range 25-200 degrees C using spectroscopic ellipsometry and synchrotron X-ray reflectivity, while the in-plane thermal expansion coefficient alpha(parallel) of each film was determined over the temperature range 25-400 degrees C by residual stress analysis. PMSSQ films cured at higher temperatures exhibited reduced thermal expansion, which is attributed to the denser molecular packing and higher degree of cross-linking that arises at higher temperatures. Surprisingly however, all the PMSSQ films were found to exhibit very strong anisotropic thermal expansion; alpha(perpendicular) and alpha(parallel) of the films were in the ranges 140-329 ppm/ degrees C and 12-29 ppm/ degrees C respectively, depending on the curing temperature. This is the first time that cured PMSSQ thin films have been shown to exhibit anisotropic thermal expansion behavior. This anisotropic thermal expansion of the PMSSQ thin films might be due to the anisotropy of cross-link density in the films, which arises because of a combination of factors: the preferential orientation of methyl groups toward the upper film surface and the preferential network formation in the film plane that occurs during curing of the confined film. In addition, the film electron densities were determined using synchrotron X-ray reflectivity measurements and the film biaxial moduli were obtained using residual stress analysis.

  14. Spin current

    CERN Document Server

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

    2012-01-01

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

  15. Recycle Glass in Foam Glass Production

    DEFF Research Database (Denmark)

    Petersen, Rasmus Rosenlund; König, Jakob; Yue, Yuanzheng

    The foam glass industry turn recycle glass into heat insulating building materials. The foaming process is relative insensitive to impurities in the recycle glass. It is therefore considered to play an important role in future glass recycling. We show and discuss trends of use of recycled glasses...... in foam glass industry and the supply sources and capacity of recycle glass....

  16. Cosmos & Glass

    DEFF Research Database (Denmark)

    Beim, Anne

    1996-01-01

    The article unfolds the architectural visions of glass by Bruno Taut. It refers to inspirations by Paul Sheerbart and litterature and the Crystal Chain, also it analyses the tectonic univers that can be found in the glass pavillion for the Werkbund exposition in Cologne.......The article unfolds the architectural visions of glass by Bruno Taut. It refers to inspirations by Paul Sheerbart and litterature and the Crystal Chain, also it analyses the tectonic univers that can be found in the glass pavillion for the Werkbund exposition in Cologne....

  17. Spin-glass behavior in single crystals of hetero-metallic magnetic warwickites MgFeBO{sub 4,} Mg{sub 0.5}Co{sub 0.5}FeBO{sub 4,} and CoFeBO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Arauzo, A., E-mail: aarauzo@unizar.es [Servicio de Medidas Físicas, Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza (Spain); Kazak, N.V. [L.V. Kirensky Institute of Physics, SB of RAS, 660036 Krasnoyarsk (Russian Federation); Ivanova, N.B. [Siberian Federal University, 660074 Krasnoyarsk (Russian Federation); Platunov, M.S. [L.V. Kirensky Institute of Physics, SB of RAS, 660036 Krasnoyarsk (Russian Federation); Knyazev, Yu.V. [Siberian Federal University, 660074 Krasnoyarsk (Russian Federation); Bayukov, O.A.; Bezmaternykh, L.N. [L.V. Kirensky Institute of Physics, SB of RAS, 660036 Krasnoyarsk (Russian Federation); Lyubutin, I.S.; Frolov, K.V. [Shubnikov Institute of Crystallography, RAS, 119333 Moscow (Russian Federation); Ovchinnikov, S.G. [L.V. Kirensky Institute of Physics, SB of RAS, 660036 Krasnoyarsk (Russian Federation); Siberian Federal University, 660074 Krasnoyarsk (Russian Federation); Siberian State Aerospace University, 660014 Krasnoyarsk (Russian Federation); Bartolomé, J. [Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza and Departamento de Física de la Materia Condensada, 50009 Zaragoza (Spain)

    2015-10-15

    Magnetic properties of heterometallic warwickites MgFeBO{sub 4,} Mg{sub 0.5}Co{sub 0.5}FeBO{sub 4,} and CoFeBO{sub 4} are presented, highlighting the effect of Co substitution on the magnetic properties of these compounds. The analysis of magnetization and heat capacity data has shown that these compounds exhibit a spin-glass transition below T{sub SG}=10, 20 and 22 K, respectively. Using zero field ac susceptibility as entanglement witness we find that the low dimensional magnetic behavior above T{sub SG} show quantum entanglement behavior χ(Τ)∝T{sup −α(Τ)} up to T{sub E}≈130 K. The α parameters have been deduced as a function of temperature and Co content, indicating the existence of random singlet phase in this temperature region. Above T{sub E} the paramagnetism is interpreted in terms of non-entangled spins giving rise to Curie–Weiss paramagnetism. The different intra- and inter-ribbon exchange interaction pathways have been calculated within a simple indirect coupling model. It is determined that the triangular motifs in the warwickite structure, together with the competing interactions, induce frustration. The spin-glass character is explained in terms of the substitutional disorder of the Mg, Fe and Co atoms at the two available crystallographic sites, and the frustration induced by the competing interactions. The Co substitution induces uniaxial anisotropy, increases the absolute magnetization and increases the spin-glass freezing temperature. The entanglement behavior is supported in the intermediate phase irrespective of the introduction of anisotropy by the Co substitution. - Highlights: • Spin-glass transition of MgFeBO{sub 4,} Mg{sub 0.5}Co{sub 0.5}FeBO{sub 4,} and CoFeBO{sub 4}. • Anisotropy and transition temperature T{sub SG} increases with Co substitution. • Dynamical scaling theory near T{sub SG} is fulfilled. • Quantum entanglement is observed in between T{sub SG} and T{sub E}=130 K. • Low dimensional random singlet phase

  18. Glass Glimpsed

    DEFF Research Database (Denmark)

    Lock, Charles

    2015-01-01

    Glass in poetry as it reflects the viewer and as its power of reflection are both reduced and enhanced by technology.......Glass in poetry as it reflects the viewer and as its power of reflection are both reduced and enhanced by technology....

  19. Experimental study of 199Hg spin anti-relaxation coatings

    CERN Document Server

    Chowdhuri, Z; Horras, M; Kirch, K; Krempel, J; Lauss, B; Mtchedlishvili, A; Rebreyend, D; Roccia, S; Schmidt-Wellenburg, P; Zsigmond, G

    2013-01-01

    We report on a comparison of spin relaxation rates in a $^{199}$Hg magnetometer using different wall coatings. A compact mercury magnetometer was built for this purpose. Glass cells coated with fluorinated materials show longer spin coherence times than if coated with their hydrogenated homologues. The longest spin relaxation time of the mercury vapor was measured with a fluorinated paraffin wall coating.

  20. Study on the Orientation of Liquid Crystals Presented on the Glass Substrates Spin-coated and Functionalized with Copper Ions%铜离子功能化的基底表面上液晶取向的研究

    Institute of Scientific and Technical Information of China (English)

    王诗鸣; 熊兴良; 张琰; 李广; 陈萌梦

    2013-01-01

    在液晶型化学与生物传感器的研究中,构建一个能使液晶分子长时间呈稳定、均一的取向排列且制作方法简易的基底表面对于传感器的实用化至关重要.本研究通过将5种不同浓度(0~ 100 mmol/L)的高氯酸铜无水乙醇溶液直接旋转喷涂于载玻片上,制备成具有化学敏感性的铜离子基底表面;随后将5CB液晶滴加在该基底表面,制作成液晶盒(液晶传感器);利用偏光显微镜的直光和锥光模式观察液晶分子的取向排列情况.实验发现在经过较短的时间后,旋涂有高氯酸铜的所有传感器的透射光斑先后逐渐变暗;高氯酸铜的浓度越大,光斑变暗的速度越快,完全变暗所需的时间越短;而未喷涂高氯酸铜的传感器在室温环境(25℃)下静置ld后,其透射光斑亮度没有变化;室温环境下于烘箱中贮存2个月后,喷涂有高氯酸铜的传感器的透射光亮度基本没有变化.结果表明,玻璃表面上直接喷涂高氯酸铜的基底表面能使液晶分子长时间呈稳定、均一的垂直排列;高氯酸铜的浓度对液晶取向排列的响应速度有影响.%A stable,uniform,easily implemented,LC-based chemical and biological sensor substrate for orientations of liquid crystals (LCs) for a long-term is urgently needed for medical applications of the sensors.We proposed a use of spin-coating of copper perchlorate (Cu (ClO4)2),with five different concentrations (0-100mmol/L),directly on glass slides for fabricating a layer of chemically-sensitive copper ions.Observing the transmitted light with a polarized microscope,we found the luminosity of the light propagated through sensors deposited with copper ions started to weaken gradually after a certain time.The higher was the concentration of copper ions covered on the glass substrates of the sensors,the faster the weakening occurred,and the less time was needed for transmitted light to turn completely dark.But there was no change in

  1. Thermodynamics of Glassy Systems: Glasses, Spin Glasses and Optimization

    NARCIS (Netherlands)

    Leuzzi, L.

    2002-01-01

    After a long, self-standing dominance of Newtonian reductionism, at the beginning of the nineteenth century, with the birth of thermodynamics, a new approach began to develop to the study of nature. Indeed, the prediction of the behaviour of a macroscopic material through the knowledge of all the Ne

  2. Thermodynamics of Glassy Systems: Glasses, Spin Glasses and Optimization

    NARCIS (Netherlands)

    Leuzzi, L.

    2002-01-01

    After a long, self-standing dominance of Newtonian reductionism, at the beginning of the nineteenth century, with the birth of thermodynamics, a new approach began to develop to the study of nature. Indeed, the prediction of the behaviour of a macroscopic material through the knowledge of all the

  3. Quantum Computational Complexity of Spin Glasses

    Science.gov (United States)

    2011-03-19

    canonical problem of classical statistical mechanics: computation of the classical partition function. We have approached this problem using the Potts...enumerator polynomial from coding theory and Z and exploited the fact that there exists a quantum algorithm for efficiently estimating Gauss sums in...computational complexity of the canonical problem of classical statistical mechanics: computation of the classical partition function. We have approached this

  4. A unified stability property in spin glasses

    CERN Document Server

    Panchenko, Dmitry

    2011-01-01

    Gibbs' measures in the Sherrington-Kirkpatrick type models satisfy two asymptotic stability properties, the Aizenman-Contucci stochastic stability and the Ghirlanda-Guerra identities, which play a fundamental role in our current understanding of these models. In this paper we show that one can combine these two properties very naturally into one unified stability property.

  5. Spin ordering in a random antiferromagnetic Heisenberg spin system: Numerical simulation

    Science.gov (United States)

    Ghazali, A.; Diep, Hung T.

    1985-04-01

    We study by a Monte Carlo method, a three-dimensional classical antiferromagnetic random Heisenberg spin system with an exchange interaction which decreases exponentially with distance. We find no indication of a spin glass transition when only isotropic exchange exists. However, a gradual spin freezing is observed as T→0. In the presence of a strong enough Ising-type uniaxial magnetic anisotropy, we observe a peak in the specific heat and a stable order parameter. However, no true thermoremanent magnetization is observed.

  6. Glass-formingproperty of hydroxyectoine is the cause of its superior function as a desiccation protectant

    NARCIS (Netherlands)

    Tanne, C.; Golovina, E.A.; Hoekstra, F.A.; Meffert, A.; Galinski, E.A.

    2014-01-01

    We were able to demonstrate that hydroxyectoine, in contrast to ectoine, is a good glass-forming compound. Fourier transform infrared and spin label electron spin resonance studies of dry ectoine and hydroxyectoine have shown that the superior glass-forming properties of hydroxyectoine result from s

  7. Spin multiplicities

    Energy Technology Data Exchange (ETDEWEB)

    Curtright, T.L., E-mail: curtright@miami.edu [Department of Physics, University of Miami, Coral Gables, FL 33124-8046 (United States); Van Kortryk, T.S., E-mail: vankortryk@gmail.com [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: zachos@anl.gov [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)

    2017-02-05

    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.

  8. Fundamental mechanical and microstructural observations in metallic glass coating production

    NARCIS (Netherlands)

    Matthews, D.T.A.; Ocelik, V.; de Hosson, J.T.M.; DeHosson, JTM; Brebbia, CA; Nishida, SI

    2005-01-01

    The production of a wide range of metallic Glass Forming Alloys (GFA) has been investigated by several processing routes including simple arc-casting and melt-spinning to form Bulk Metallic Glasses (BMG). The concepts surrounding such alloys have been directed towards the production of thick (> 300

  9. Fundamental mechanical and microstructural observations in metallic glass coating production

    NARCIS (Netherlands)

    Matthews, D.T.A.; Ocelik, V.; de Hosson, J.T.M.; DeHosson, JTM; Brebbia, CA; Nishida, SI

    2005-01-01

    The production of a wide range of metallic Glass Forming Alloys (GFA) has been investigated by several processing routes including simple arc-casting and melt-spinning to form Bulk Metallic Glasses (BMG). The concepts surrounding such alloys have been directed towards the production of thick (> 300

  10. High-spin and low-spin states in Invar and related alloys

    Science.gov (United States)

    Moruzzi, V. L.

    1990-04-01

    Total-energy band calculations that show the coexistence of a high-spin and low-spin state in fcc transition metals and alloys are presented. The energy difference between the two states is shown to be a function of the electron concentration and to vanish at 8.6. At larger electron concentrations the low-temperature state is the high-spin state, and the thermal expansion is shown to pause at a system-dependent characteristic temperature. At lower electron concentrations the low-temperature state is the low-spin state, and enhanced thermal expansion is expected. An analysis that leads to a qualitative understanding of the thermal properties of Invar and that implies a connection with martensitic transformations and spin glasses in related alloys is presented. For Invar a magnetic collapse from the high-spin to the low-spin state at a pressure of 55 kbar is predicted.

  11. Spin foams

    CERN Document Server

    Engle, Jonathan

    2013-01-01

    The spin foam framework provides a way to define the dynamics of canonical loop quantum gravity in a spacetime covariant way, by using a path integral over histories of quantum states which can be interpreted as `quantum space-times'. This chapter provides a basic introduction to spin foams aimed principally at beginning graduate students and, where possible, at broader audiences.

  12. Ising spins on thin graphs

    CERN Document Server

    Baillie, C F; Kownacki, J P

    1994-01-01

    The Ising model on ``thin'' graphs (standard Feynman diagrams) displays several interesting properties. For ferromagnetic couplings there is a mean field phase transition at the corresponding Bethe lattice transition point. For antiferromagnetic couplings the replica trick gives some evidence for a spin glass phase. In this paper we investigate both the ferromagnetic and antiferromagnetic models with the aid of simulations. We confirm the Bethe lattice values of the critical points for the ferromagnetic model on \\phi^3 and \\phi^4 graphs and examine the putative spin glass phase in the antiferromagnetic model by looking at the overlap between replicas in a quenched ensemble of graphs. We also compare the Ising results with those for higher state Potts models and Ising models on ``fat'' graphs, such as those used in 2D gravity simulations.

  13. Nanoparticle-textured surfaces from spin coating.

    Science.gov (United States)

    Weiss, R A; Zhai, X; Dobrynin, A V

    2008-05-20

    Rough surfaces composed of discrete but relatively uniform nanoparticles were prepared from a lightly sulfonated polystyrene ionomer by spin coating from tetrahydrofuran (THF) or a THF/methanol mixture onto a silica surface. The particle morphology is consistent with the spinodal decomposition of the film surface occurring during spin coating. The particles are well wetted to the silica, and if heated for a long time above the ionomer's glass-transition temperature, the particles flow and coalesce into a smooth, homogeneous film.

  14. Spin dynamics and spin freezing at ferromagnetic quantum phase transitions

    Science.gov (United States)

    Schmakat, P.; Wagner, M.; Ritz, R.; Bauer, A.; Brando, M.; Deppe, M.; Duncan, W.; Duvinage, C.; Franz, C.; Geibel, C.; Grosche, F. M.; Hirschberger, M.; Hradil, K.; Meven, M.; Neubauer, A.; Schulz, M.; Senyshyn, A.; Süllow, S.; Pedersen, B.; Böni, P.; Pfleiderer, C.

    2015-07-01

    We report selected experimental results on the spin dynamics and spin freezing at ferromagnetic quantum phase transitions to illustrate some of the most prominent escape routes by which ferromagnetic quantum criticality is avoided in real materials. In the transition metal Heusler compound Fe2TiSn we observe evidence for incipient ferromagnetic quantum criticality. High pressure studies in MnSi reveal empirical evidence for a topological non-Fermi liquid state without quantum criticality. Single crystals of the hexagonal Laves phase compound Nb1- y Fe2+ y provide evidence of a ferromagnetic to spin density wave transition as a function of slight compositional changes. Last but not least, neutron depolarisation imaging in CePd1- x Rh x underscore evidence taken from the bulk properties of the formation of a Kondo cluster glass.

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

    Directory of Open Access Journals (Sweden)

    Saburo Takahashi and Sadamichi Maekawa

    2008-01-01

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

  16. Spin electronics

    CERN Document Server

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

    2004-01-01

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

  17. Magneto-optical properties of transparent divalent iron phosphate glasses

    OpenAIRE

    Akamatsu, Hirofumi; FUJITA, KOJI; Murai, Shunsuke; Tanaka, Katsuhisa

    2008-01-01

    We have prepared glasses having xFeO·(100−x)P2O5 (mol %) (x=50.0, 54.0, 57.1) compositions by melting under mild reducing condition and found that these glasses exhibit fairly high transmittance in the visible range and large Faraday effect at the wavelength of about 400 nm. 57Fe Mössbauer spectra confirm that almost all the iron ions are present as Fe2+ in the glasses. A spin glass transition is observed at low temperatures in the temperature dependence of magnetic susceptibility. Intense op...

  18. Negative spontaneous magnetization and semi-spin glass magnetic order in mixed spinel Co{sub 0.6}Zn{sub 0.4}Fe{sub 1.7}Mn{sub 0.3}O{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Arti; Tandon, R. P. [Department of Physics and Astrophysics, University of Delhi, Delhi-110007 (India); Shinde, A. B.; Krishna, P. S. R. [Bhabha Atomic Research Centre, Mumbai (India); Chatterjee, Ratnamala, E-mail: rmala@physics.iitd.ac.in [Department of Physics, Indian Institute of Technology, Delhi (India)

    2015-10-07

    In this paper, we establish the negative spontaneous magnetization in Mn and Zn substituted cobalt ferrite Co{sub 0.6}Zn{sub 0.4}Fe{sub 1.7}Mn{sub 0.3}O{sub 4} (CZFMO). It is suggested that the origin of negative spontaneous magnetization is due to the substitution of small sized Mn{sup +4} ions (compared to Fe{sup +3} ions) at the octahedral B site in compound Co{sub 0.6}Zn{sub 0.4} Fe{sub 2}O{sub 4}. The low value of Poisson's ratio ∼0.202 for this compound possibly contributes towards the easy distortion in the bond length and bond angle, causing increase in Fe-O bond distance/decrease in Fe-O-Fe bond angle with Mn substitution, leading to considerably weak Fe-O-Fe superexchange interaction at the octahedral B site. The neutron diffraction data clearly illustrated the significant reduction in ordered magnetic moment at the B site, with the resultant negative spontaneous magnetization (M = M{sub B} − M{sub A}) in this mixed spinel system. The spin disorder also gives rise to an interesting semi-spin glass behavior in CZFMO.

  19. Classical gravitational spin-spin interaction

    OpenAIRE

    Bonnor, W. B.

    2002-01-01

    I obtain an exact, axially symmetric, stationary solution of Einstein's equations for two massless spinning particles. The term representing the spin-spin interaction agrees with recently published approximate work. The spin-spin force appears to be proportional to the inverse fourth power of the coordinate distance between the particles.

  20. Spin-Orbit induced semiconductor spin guides

    OpenAIRE

    Valin-Rodriguez, Manuel; Puente, Antonio; Serra, Llorens

    2002-01-01

    The tunability of the Rashba spin-orbit coupling allows to build semiconductor heterostructures with space modulated coupling intensities. We show that a wire-shaped spin-orbit modulation in a quantum well can support propagating electronic states inside the wire only for a certain spin orientation and, therefore, it acts as an effective spin transmission guide for this particular spin orientation.

  1. Glass Fibers: Quo Vadis?

    Directory of Open Access Journals (Sweden)

    Edith Mäder

    2017-02-01

    Full Text Available Since the early 1930s, the process of melting glass and subsequently forming fibers, in particular discontinuous fiber glass or continuous glass filaments, evolved into commercial-scale manufacturing.[...

  2. Gamma radiation induced changes in nuclear waste glass containing Eu

    Science.gov (United States)

    Mohapatra, M.; Kadam, R. M.; Mishra, R. K.; Kaushik, C. P.; Tomar, B. S.; Godbole, S. V.

    2011-10-01

    Gamma radiation induced changes were investigated in sodium-barium borosilicate glasses containing Eu. The glass composition was similar to that of nuclear waste glasses used for vitrifying Trombay research reactor nuclear waste at Bhabha Atomic Research Centre, India. Photoluminescence (PL) and electron paramagnetic resonance (EPR) techniques were used to study the speciation of the rare earth (RE) ion in the matrix before and after gamma irradiation. Judd-Ofelt ( J- O) analyses of the emission spectra were done before and after irradiation. The spin counting technique was employed to quantify the number of defect centres formed in the glass at the highest gamma dose studied. PL data suggested the stabilisation of the trivalent RE ion in the borosilicate glass matrix both before and after irradiation. It was also observed that, the RE ion distributes itself in two different environments in the irradiated glass. From the EPR data it was observed that, boron oxygen hole centre based radicals are the predominant defect centres produced in the glass after irradiation along with small amount of E’ centres. From the spin counting studies the concentration of defect centres in the glass was calculated to be 350 ppm at 900 kGy. This indicated the fact that bulk of the glass remained unaffected after gamma irradiation up to 900 kGy.

  3. CRYSTALLIZATION IN MULTICOMPONENT GLASSES

    Energy Technology Data Exchange (ETDEWEB)

    KRUGER AA; HRMA PR

    2009-10-08

    In glass processing situations involving glass crystallization, various crystalline forms nucleate, grow, and dissolve, typically in a nonuniform temperature field of molten glass subjected to convection. Nuclear waste glasses are remarkable examples of multicomponent vitrified mixtures involving partial crystallization. In the glass melter, crystals form and dissolve during batch-to-glass conversion, melter processing, and product cooling. Crystals often agglomerate and sink, and they may settle at the melter bottom. Within the body of cooling glass, multiple phases crystallize in a non-uniform time-dependent temperature field. Self-organizing periodic distribution (the Liesegnang effect) is common. Various crystallization phenomena that occur in glass making are reviewed.

  4. Finite size effects and spin transition in ball-milled γ-(FeMn) 30Cu 70 nanostructured alloys

    Science.gov (United States)

    Restrepo, J.; Greneche, J. M.; González, J. M.

    2004-12-01

    Fe 15Mn 15Cu 70 alloys were prepared by high-energy ball milling over a wide range of grinding times from 15 min to 72 h. The corresponding magnetic properties were followed by means of vibrating sample magnetometry, magnetic susceptibility and Mössbauer spectroscopy. By using a Rietveld structural analysis of high-resolution X-ray diffraction data, lattice parameter and grain size correlations with magnetization and coercive force were carried out. Results revealed a strong microstructural dependence of the magnetic properties with the grain size, resembling a finite size-driven magnetic transition at a critical crystallite value of around 8.5 nm. This behavior is endorsed by a partial low- to high-spin transition according to isomer shift results, at a critical unit-cell volume of around 50 Å 3 at 77 K attributed to strong local variations of the interatomic spacing as a consequence of the employed ball-milling procedure. Finally, as concerns to temperature behavior, samples exhibited a freezing temperature at around 61 K and a wide distribution of relaxation times ascribed to the presence of interacting CuMn and FeMnCu clusters.

  5. A spin cell for spin current.

    Science.gov (United States)

    Sun, Qing-feng; Guo, Hong; Wang, Jian

    2003-06-27

    We propose and investigate a spin-cell device which provides the necessary spin-motive force to drive a spin current for future spintronic circuits. Our spin cell has four basic characteristics: (i) it has two poles so that a spin current flows in from one pole and out from the other pole, and in this way a complete spin circuit can be established; (ii) it has a source of energy to drive the spin current; (iii) it maintains spin coherence so that a sizable spin current can be delivered; (iv) it drives a spin current without a charge current. The proposed spin cell for spin current should be realizable using technologies presently available.

  6. Free-Energy Bounds for Hierarchical Spin Models

    Science.gov (United States)

    Castellana, Michele; Barra, Adriano; Guerra, Francesco

    2014-04-01

    In this paper we study two non-mean-field (NMF) spin models built on a hierarchical lattice: the hierarchical Edward-Anderson model (HEA) of a spin glass, and Dyson's hierarchical model (DHM) of a ferromagnet. For the HEA, we prove the existence of the thermodynamic limit of the free energy and the replica-symmetry-breaking (RSB) free-energy bounds previously derived for the Sherrington-Kirkpatrick model of a spin glass. These RSB mean-field bounds are exact only if the order-parameter fluctuations (OPF) vanish: given that such fluctuations are not negligible in NMF models, we develop a novel strategy to tackle part of OPF in hierarchical models. The method is based on absorbing part of OPF of a block of spins into an effective Hamiltonian of the underlying spin blocks. We illustrate this method for DHM and show that, compared to the mean-field bound for the free energy, it provides a tighter NMF bound, with a critical temperature closer to the exact one. To extend this method to the HEA model, a suitable generalization of Griffith's correlation inequalities for Ising ferromagnets is needed: since correlation inequalities for spin glasses are still an open topic, we leave the extension of this method to hierarchical spin glasses as a future perspective.

  7. Recycling of Glass

    DEFF Research Database (Denmark)

    Christensen, Thomas Højlund; Damgaard, Anders

    2011-01-01

    system; this glass though has a long lifetime before ending up in the waste. Altogether these product types add up to 82% of the production of the European glass industry (IPCC, 2001). Recycling of glass in terms of cleaning and refilling of bottles as well as the use of broken glass in the production......Glass is used for many purposes, but in the waste system glass is predominantly found in terms of beverage and food containers with a relatively short lifetime before ending up in the waste. Furthermore there is a large amount of flat glass used in building materials which also ends up in the waste...... of new glass containers is well established in the glass industry. This chapter describes briefly howglass is produced and howwaste glass is recycled in the industry. Quality requirements and use of recycled products are discussed, as are the resource and environmental issues of glass recycling....

  8. Recycling of Glass

    DEFF Research Database (Denmark)

    Christensen, Thomas Højlund; Damgaard, Anders

    2011-01-01

    Glass is used for many purposes, but in the waste system glass is predominantly found in terms of beverage and food containers with a relatively short lifetime before ending up in the waste. Furthermore there is a large amount of flat glass used in building materials which also ends up in the waste...... system; this glass though has a long lifetime before ending up in the waste. Altogether these product types add up to 82% of the production of the European glass industry (IPCC, 2001). Recycling of glass in terms of cleaning and refilling of bottles as well as the use of broken glass in the production...... of new glass containers is well established in the glass industry. This chapter describes briefly howglass is produced and howwaste glass is recycled in the industry. Quality requirements and use of recycled products are discussed, as are the resource and environmental issues of glass recycling....

  9. Spin squeezing in nonlinear spin coherent states

    OpenAIRE

    Wang, Xiaoguang

    2001-01-01

    We introduce the nonlinear spin coherent state via its ladder operator formalism and propose a type of nonlinear spin coherent state by the nonlinear time evolution of spin coherent states. By a new version of spectroscopic squeezing criteria we study the spin squeezing in both the spin coherent state and nonlinear spin coherent state. The results show that the spin coherent state is not squeezed in the x, y, and z directions, and the nonlinear spin coherent state may be squeezed in the x and...

  10. Cavity spin optodynamics

    CERN Document Server

    Brahms, N

    2010-01-01

    The dynamics of a large quantum spin coupled parametrically to an optical resonator is treated in analogy with the motion of a cantilever in cavity optomechanics. New spin optodynamic phenonmena are predicted, such as cavity-spin bistability, optodynamic spin-precession frequency shifts, coherent amplification and damping of spin, and the spin optodynamic squeezing of light.

  11. Glass-forming property of hydroxyectoine is the cause of its superior function as a desiccation protectant

    OpenAIRE

    Erwin Arno Galinski; Christoph eTanne; Andrea eMeffert; Golovina, Elena A; Hoekstra, Folkert A.

    2014-01-01

    We were able to demonstrate that hydroxyectoine, in contrast to ectoine, is a good glass-forming compound. Fourier transform infrared (FTIR) and spin label electron spin resonance (ESR) studies of dry ectoine and hydroxyectoine have shown that the superior glass-forming properties of hydroxyectoine result from stronger intermolecular H-bonds with the OH group of hydroxyectoine. Spin probe experiments have also shown that better molecular immobilization in dry hydroxyectoine provides better re...

  12. Out-of-equilibrium dynamics in superspin glass state of strongly interacting magnetic nanoparticle assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Nakamae, Sawako, E-mail: Sawako.nakamae@cea.fr

    2014-04-15

    Interacting magnetic nanoparticles display a wide variety of magnetic behaviors ranging from modified superparamagnetism, superspin glass to possibly, superferromagnetism. The superspin glass state is described by its slow and out-of-equilibrium magnetic behaviors akin to those found in atomic spin glasses. In this article, recent experimental findings on superspin correlation length growth and the violation of the fluctuation-dissipation theorem obtained in concentrated frozen ferrofluids are presented to illustrate certain out-of-equilibrium dynamics behavior in superspin glasses. - Highlights: • Recent experimental findings on superspin glass dynamics in magnetic nanoparticle systems. • Advantages of magnetic nanoparticles for the study of spin glass physics. • Open questions and future directions in superspin glass research.

  13. Spin freezing in the spin-liquid compound FeAl2O4

    Science.gov (United States)

    Nair, Harikrishnan S.; Ramesh Kumar, K.; Strydom, André M.

    2015-02-01

    Spin freezing in the A -site spinel FeAl2O4 , which is a spin-liquid candidate, is studied using remnant magnetization and nonlinear magnetic susceptibility and isofield cooling and heating protocols. The remnant magnetization behavior of FeAl2O4 differs significantly from that of a canonical spin glass, which is also supported by analysis of the nonlinear magnetic susceptibility term χ3(T ) . Through the power-law analysis of χ3(T ) , a spin-freezing temperature Tg=11.4 ±0.9 K and critical exponent γ =1.48 ±0.59 are obtained. A Cole-Cole analysis of magnetic susceptibility shows the presence of broad spin relaxation times in FeAl2O4 , however, the irreversible dc susceptibility plot discourages an interpretation based on conventional spin-glass features. The magnetization measured using the cooling-and-heating-in-unequal-fields protocol brings more insight into the magnetic nature of this frustrated magnet and reveals unconventional glassy behavior. Combining our results, we arrive at the conclusion that the present sample of FeAl2O4 consists of a majority spin-liquid phase with "glassy" regions embedded.

  14. Glass-silicon column

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Conrad M.

    2003-12-30

    A glass-silicon column that can operate in temperature variations between room temperature and about 450.degree. C. The glass-silicon column includes large area glass, such as a thin Corning 7740 boron-silicate glass bonded to a silicon wafer, with an electrode embedded in or mounted on glass of the column, and with a self alignment silicon post/glass hole structure. The glass/silicon components are bonded, for example be anodic bonding. In one embodiment, the column includes two outer layers of silicon each bonded to an inner layer of glass, with an electrode imbedded between the layers of glass, and with at least one self alignment hole and post arrangement. The electrode functions as a column heater, and one glass/silicon component is provided with a number of flow channels adjacent the bonded surfaces.

  15. Super-Potts glass: A disordered model for glass-forming liquids

    Science.gov (United States)

    Angelini, Maria Chiara; Biroli, Giulio

    2014-12-01

    We introduce a disordered system, the super-Potts model, which is a more frustrated version of the Potts glass. Its elementary degrees of freedom are variables that can take M values and are coupled via pairwise interactions. Its exact solution on a completely connected lattice demonstrates that, for large enough M , it belongs to the class of mean-field systems solved by a one-step replica symmetry breaking ansatz. Numerical simulations by the parallel tempering technique show that in three dimensions it displays a phenomenological behavior similar to the one of glass-forming liquids. The super-Potts glass is therefore a disordered model allowing one to perform extensive and detailed studies of the random first-order transition in finite dimensions. We also discuss its behavior for small values of M , which is similar to the one of spin glasses in a field.

  16. MEASUREMENTS OF CHAIN INTERPENETRATION OF POLYMER GLASSES

    Institute of Scientific and Technical Information of China (English)

    Min-zhi Chen; Xiao-liang Wang; Fang-fang Tao; Qi Xue; Ping-chuan Sun

    2007-01-01

    The concept of entanglement provides the basis of our current understanding of the flow behavior of polymer melts. Current techniques developed to investigate the degree of interpenetration of polymer chains only provide indirectly the information of the degree of entanglement in a relatively large scale (several to tens of nanometer). In this article, we report 1H-NMR spectroscopy with dipolar filters under fast magic angle spinning for probing chain interpenetration of polymer glasses at the molecular level.

  17. Spin-Circuit Representation of Spin Pumping

    Science.gov (United States)

    Roy, Kuntal

    2017-07-01

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

  18. Nonlinear magnetic susceptibility and the spin glass state in the new nonstoichiometric spinel compounds Cu{sub 1+x}Cr{sub 1.5+y}Sb{sub 0.5+z}Se{sub 4+t} (where -0.02 {<=} x {<=} 0.01, 0.03 {<=} y {<=} 0.35, -0.2 {<=} z {<=} - 0.02, 0.01 {<=} t {<=} 0.08)

    Energy Technology Data Exchange (ETDEWEB)

    Krok-Kowalski, J. [University of Silesia, Institute of Physics, ul. Uniwersytecka 4, 40007 Katowice (Poland); Warczewski, J. [University of Silesia, Institute of Physics, ul. Uniwersytecka 4, 40007 Katowice (Poland)]. E-mail: warcz@us.edu.pl; Duda, H. [University of Silesia, Institute of Physics, ul. Uniwersytecka 4, 40007 Katowice (Poland); Gusin, P. [University of Silesia, Institute of Physics, ul. Uniwersytecka 4, 40007 Katowice (Poland); Krajewski, K. [University of Silesia, Institute of Physics, ul. Uniwersytecka 4, 40007 Katowice (Poland); Sliwinska, T. [University of Silesia, Institute of Physics, ul. Uniwersytecka 4, 40007 Katowice (Poland); Pacyna, A. [Institute of Nuclear Physics, ul. Radzikowskiego 152, 31342 Krakow (Poland); Mydlarz, T. [International Laboratory of High Magnetic Fields and Low Temperatures, ul. Gajowicka 95, 53529 Wroclaw (Poland); Malicka, E. [University of Silesia, Institute of Chemistry, ul. Szkolna 9, 40006 Katowice (Poland); Kita, A. [University of Silesia, Institute of Chemistry, ul. Szkolna 9, 40006 Katowice (Poland)

    2007-03-14

    New nonstoichiometric spinel compounds Cu{sub 1+x}Cr{sub 1.5+y}Sb{sub 0.5+z}Se{sub 4+t} (where -0.02 {<=} x {<=} 0.01, 0.03 {<=} y {<=} 0.35, -0.2 {<=} z {<=} -0.02, 0.01 {<=} t {<=} 0.08) have been obtained with the aid of the solid-phase synthesis from the stoichiometric mixtures of the constituent elements. Six samples of these compounds with the different compositions have been chosen to the dc and ac magnetic susceptibility measurements. From the analysis of these measurements spin glass states have been revealed with the spin freezing temperature about 70 K for all the six samples. The magnetization measurements were performed for the same samples with the use of the induction method in the high stationary magnetic fields up to 14 T in the temperature range of 4.2-273 K. No sample under study reaches the saturation magnetization even at 14 T though they display a spontaneous magnetization, the latter existing at least up to 273 K. The temperature dependence of the dc inverse molar magnetic susceptibility reveals two different rectilinear parts which can be interpreted as related to two different Curie-Weiss temperatures: {approx}68 and {approx}45 K. It seems that these two temperatures correspond to two different types of the magnetically ordered clusters. The average effective magnetic moment is here equal to 2.35{mu} {sub B}/ion pointing to the high defectiveness of both the crystal and magnetic structures. All the effects observed on both the magnetization and inverse molar magnetic susceptibility curves point to the appearance of the cluster spin glass states in the samples under study. Generally speaking, it is the statistical character of the substitution of the nonmagnetic antimony ions instead of the magnetic chromium ions which leads to the frustration of the orientations of the localized magnetic moments in the samples under study and in the consequence to the appearance of the spin glass states.

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

    Science.gov (United States)

    Rückriegel, Andreas; Kopietz, Peter

    2017-03-01

    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.

  20. lead glass brick

    CERN Multimedia

    When you look through the glass at a picture behind, the picture appears raised up because light is slowed down in the dense glass. It is this density (4.06 gcm-3) that makes lead glass attractive to physicists. The refractive index of the glass is 1.708 at 400nm (violet light), meaning that light travels in the glass at about 58% its normal speed. At CERN, the OPAL detector uses some 12000 blocks of glass like this to measure particle energies.

  1. Aging, memory, and nonhierarchical energy landscape of spin jam

    Science.gov (United States)

    Samarakoon, Anjana; Sato, Taku J.; Chen, Tianran; Chern, Gai-Wei; Yang, Junjie; Klich, Israel; Sinclair, Ryan; Zhou, Haidong; Lee, Seung-Hun

    2016-10-01

    The notion of complex energy landscape underpins the intriguing dynamical behaviors in many complex systems ranging from polymers, to brain activity, to social networks and glass transitions. The spin glass state found in dilute magnetic alloys has been an exceptionally convenient laboratory frame for studying complex dynamics resulting from a hierarchical energy landscape with rugged funnels. Here, we show, by a bulk susceptibility and Monte Carlo simulation study, that densely populated frustrated magnets in a spin jam state exhibit much weaker memory effects than spin glasses, and the characteristic properties can be reproduced by a nonhierarchical landscape with a wide and nearly flat but rough bottom. Our results illustrate that the memory effects can be used to probe different slow dynamics of glassy materials, hence opening a window to explore their distinct energy landscapes.

  2. Microstructuring of glasses

    CERN Document Server

    Hülsenberg, Dagmar; Bismarck, Alexander

    2008-01-01

    As microstructured glass becomes increasingly important for microsystems technology, the main application fields include micro-fluidic systems, micro-analysis systems, sensors, micro-actuators and implants. And, because glass has quite distinct properties from silicon, PMMA and metals, applications exist where only glass devices meet the requirements. The main advantages of glass derive from its amorphous nature, the precondition for its - theoretically - direction-independent geometric structurability. Microstructuring of Glasses deals with the amorphous state, various glass compositions and their properties, the interactions between glasses and the electromagnetic waves used to modify it. Also treated in detail are methods for influencing the geometrical microstructure of glasses by mechanical, chemical, thermal, optical, and electrical treatment, and the methods and equipment required to produce actual microdevices.

  3. Finite size effects and spin transition in ball-milled {gamma}-(FeMn){sub 30}Cu{sub 70} nanostructured alloys

    Energy Technology Data Exchange (ETDEWEB)

    Restrepo, J. [Grupo de Estado Solido, Instituto de Fisica, Universidad de Antioquia, A. A. 1226, Medellin (Colombia)]. E-mail: jrestre@fisica.udea.edu.co; Greneche, J.M. [Laboratoire de Physique de l' Etat Condense, UMR CNRS 6087, Universite du Maine, 72085 Le Mans, Cedex 9 (France); Gonzalez, J.M. [Instituto de Magnetismo Aplicado, P.O. Box 155. 28230 Las Rozas, Madrid (Spain)

    2004-12-31

    Fe{sub 15}Mn{sub 15}Cu{sub 70} alloys were prepared by high-energy ball milling over a wide range of grinding times from 15 min to 72 h. The corresponding magnetic properties were followed by means of vibrating sample magnetometry, magnetic susceptibility and Moessbauer spectroscopy. By using a Rietveld structural analysis of high-resolution X-ray diffraction data, lattice parameter and grain size correlations with magnetization and coercive force were carried out. Results revealed a strong microstructural dependence of the magnetic properties with the grain size, resembling a finite size-driven magnetic transition at a critical crystallite value of around 8.5 nm. This behavior is endorsed by a partial low- to high-spin transition according to isomer shift results, at a critical unit-cell volume of around 50 A{sup 3} at 77 K attributed to strong local variations of the interatomic spacing as a consequence of the employed ball-milling procedure. Finally, as concerns to temperature behavior, samples exhibited a freezing temperature at around 61 K and a wide distribution of relaxation times ascribed to the presence of interacting CuMn and FeMnCu clusters.

  4. Relativistic Spin Operators

    Institute of Scientific and Technical Information of China (English)

    ZHANG Peng-Fei; RUAN Tu-Nan

    2001-01-01

    A systematic theory on the appropriate spin operators for the relativistic states is developed. For a massive relativistic particle with arbitrary nonzero spin, the spin operator should be replaced with the relativistic one, which is called in this paper as moving spin. Further the concept of moving spin is discussed in the quantum field theory. A new is constructed. It is shown that, in virtue of the two operators, problems in quantum field concerned spin can be neatly settled.

  5. Infrared Transparent Selenide Glasses.

    Science.gov (United States)

    1997-03-14

    crystalline halides, silica and fluoride glasses, and chalcogenide glasses. Crystalline halides undergo plastic deformation and are hygroscopic...mainly for applications operating at wavelengths less than 3 microns. Silicate and fluoride glasses have been developed as optical fiber amplifiers...activity. Preferred rare earths includes praseodymium, neodymium, erbium, cerium , dysprosium, holmium, thulium, terbium, ytterbium or mixtures of

  6. Self-organized criticality in glassy spin systems requires long-range interactions

    Science.gov (United States)

    Andresen, Juan Carlos; Andrist, Ruben S.; Katzgraber, Helmut G.; Dobrosavljevic, Vladimir; Zimanyi, Gergerly T.

    2013-03-01

    We investigate the conditions required for general spin systems with frustration and disorder to display self-organized criticality, a property which so far has been established in spin models only for the infinite-range Sherringtion-Kirkpatrick Ising spin-glass model [PRL 83, 1034 (1999)]. We study the avalanche and the magnetization jump distribution triggered by an external magnetic field in the short-range Edward-Anderson Ising spin glass for various space dimensions, between 2 and 8. Our numerical results, obtained on systems of unprecedented size, demonstrate that self-organized criticality is recovered only in the strict limit of infinite space dimensions (or equivalently of long-ranged interaction), and is not a generic property of spin-glass models in finite space dimensions.

  7. Generalized approach to non-exponential relaxation

    Indian Academy of Sciences (India)

    R M Pickup; R Cywinski; C Pappas; P Fouquet; B Farago; P Falus

    2008-11-01

    Non-exponential relaxation is a universal feature of systems as diverse as glasses, spin glasses, earthquakes, financial markets and the universe. Complex relaxation results from hierarchically constrained dynamics with the strength of the constraints being directly related to the form of the relaxation, which changes from a simple exponential to a stretched exponential and a power law by increasing the constraints in the system. A global and unified approach to non-exponentiality was first achieved by Weron and was further generalized by Brouers and Sotolongo-Costa, who applied the concept of non-extensive entropy introduced by Tsallis to the relaxation of disordered systems. These concepts are now confronted with experimental results on the classical metallic spin glasses CuMn, AuFe and the insulating system EuSrS. The revisited data have also be complemented by new results on several compositions of the classical CuMn spin glass and on systems, like CoGa and CuCo, the magnetic behaviour of which is believed to arise from magnetic clusters and should be characteristic for superparamagnetism.

  8. Spectroscopic studies of lead halo borate glasses

    Science.gov (United States)

    Sekhar, K. Chandra; Hameed, Abdul; Chary, M. Narasimha; Shareefuddin, Md.

    2015-06-01

    Glasses in the system xPbF2-(30-x) PbO-69B2O3-1CuO (x=5, 10, 15, 20, & 25 mole %) were prepared by melt quenching method and they are characterized by XRD to confirm the glassy nature. Electron Paramagnetic Resonance (EPR) studies at room temperature in the X-band frequencies and FTIR studies on prepared glass systems were reported. The non-linear variation of spin-Hamiltonian parameters with PbF2 content indicated the change in the ligand field strength around Cu2+ ions in the host glass. The ground state of Cu2+ ions in the glass is designated as dx2-y2 orbital (2B1g) while the observed symmetry around it is tetragonally distorted octahedral. The molecular orbital coefficients α2, β2 and β12 are evaluated for Cu2+ doped samples. From the FTIR studies it was observed that the glass made up of BO3 and BO4 units.

  9. Event-chain Monte Carlo for classical continuous spin models

    Science.gov (United States)

    Michel, Manon; Mayer, Johannes; Krauth, Werner

    2015-10-01

    We apply the event-chain Monte Carlo algorithm to classical continuum spin models on a lattice and clarify the condition for its validity. In the two-dimensional XY model, it outperforms the local Monte Carlo algorithm by two orders of magnitude, although it remains slower than the Wolff cluster algorithm. In the three-dimensional XY spin glass model at low temperature, the event-chain algorithm is far superior to the other algorithms.

  10. Fluoride glass fiber optics

    CERN Document Server

    Aggarwal, Ishwar D

    1991-01-01

    Fluoride Glass Fiber Optics reviews the fundamental aspects of fluoride glasses. This book is divided into nine chapters. Chapter 1 discusses the wide range of fluoride glasses with an emphasis on fluorozirconate-based compositions. The structure of simple fluoride systems, such as BaF2 binary glass is elaborated in Chapter 2. The third chapter covers the intrinsic transparency of fluoride glasses from the UV to the IR, with particular emphasis on the multiphonon edge and electronic edge. The next three chapters are devoted to ultra-low loss optical fibers, reviewing methods for purifying and

  11. Multiple Glass Ceilings

    OpenAIRE

    Russo, Giovanni; Hassink, Wolter

    2011-01-01

    Both vertical (between job levels) and horizontal (within job levels) mobility can be sources of wage growth. We find that the glass ceiling operates at both margins. The unexplained part of the wage gap grows across job levels (glass ceiling at the vertical margin) and across the deciles of the intra-job-level wage distribution (glass ceiling at the horizontal margin). This implies that women face many glass ceilings, one for each job level above the second, and that the glass ceiling is a p...

  12. Reprint of: Out-of-equilibrium dynamics in superspin glass state of strongly interacting magnetic nanoparticle assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Nakamae, Sawako, E-mail: Sawako.nakamae@cea.fr

    2014-11-15

    Interacting magnetic nanoparticles display a wide variety of magnetic behaviors ranging from modified superparamagnetism, superspin glass to possibly, superferromagnetism. The superspin glass state is described by its slow and out-of-equilibrium magnetic behaviors akin to those found in atomic spin glasses. In this article, recent experimental findings on superspin correlation length growth and the violation of the fluctuation-dissipation theorem obtained in concentrated frozen ferrofluids are presented to illustrate certain out-of-equilibrium dynamics behavior in superspin glasses. - Highlights: • Recent experimental findings on superspin glass dynamics in magnetic nanoparticle systems. • Advantages of magnetic nanoparticles for the study of spin glass physics. • Open questions and future directions in superspin glass research.

  13. Magnetic Nanostructures Spin Dynamics and Spin Transport

    CERN Document Server

    Farle, Michael

    2013-01-01

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

  14. Spin dynamics in geometrically frustrated antiferromagnetic pyrochlores

    Science.gov (United States)

    Gardner, J. S.; Ehlers, G.; Bramwell, S. T.; Gaulin, B. D.

    2004-03-01

    We have studied the spin dynamics of several antiferromagnetic pyrochlore oxides. These magnets are geometrically frustrated and only reach their ground states at temperatures much lower than that expected from mean field theory. Here we present data on the magnetic nature, especially the spin dynamics of Tb2Ti2O7, Gd2Ti2O7 and Y2Mo2O7. In these systems the ground states are found to be very different. Y2Mo2O7 freezes completely into a spin glass-like state, Tb2Ti2O7 is a cooperative paramagnetic and remains dynamic down to 15 mK and Gd2Ti2O7 enters a unique partially ordered state at {\\sim }1 K.

  15. Stripe glasses in ferromagnetic thin films

    Science.gov (United States)

    Principi, Alessandro; Katsnelson, Mikhail I.

    2016-02-01

    Domain walls in magnetic multilayered systems can exhibit a very complex and fascinating behavior. For example, the magnetization of thin films of hard magnetic materials is in general perpendicular to the thin-film plane, thanks to the strong out-of-plane anisotropy, but its direction changes periodically, forming an alternating spin-up and spin-down stripe pattern. The latter is stabilized by the competition between the ferromagnetic coupling and dipole-dipole interactions, and disappears when a moderate in-plane magnetic field is applied. It has been suggested that such a behavior may be understood in terms of a self-induced stripe glassiness. In this paper we show that such a scenario is compatible with the experimental findings. The strong out-of-plane magnetic anisotropy of the film is found to be beneficial for the formation of both stripe-ordered and glassy phases. At zero magnetic field the system can form a glass only in a narrow interval of fairly large temperatures. An in-plane magnetic field, however, shifts the glass transition towards lower temperatures, therefore enabling it at or below room temperature. In good qualitative agreement with the experimental findings, we show that a moderate in-plane magnetic field of the order of 50 mT can lead to the formation of defects in the stripe pattern, which sets the onset of the glass transition.

  16. Glass and glass-ceramic photonic systems

    Science.gov (United States)

    Zur, Lidia; Thi Ngoc Tran, Lam; Meneghetti, Marcello; Varas, Stefano; Armellini, Cristina; Ristic, Davor; Chiasera, Alessandro; Scotognella, Francesco; Pelli, Stefano; Nunzi Conti, Gualtiero; Boulard, Brigitte; Zonta, Daniele; Dorosz, Dominik; Lukowiak, Anna; Righini, Giancarlo C.; Ramponi, Roberta; Ferrari, Maurizio

    2017-02-01

    The development of optically confined structure is a major topic in both basic and applied physics not solely ICT oriented but also concerning lighting, laser, sensing, energy, environment, biological and medical sciences, and quantum optics. Glasses and glass-ceramics activated by rare earth ions are the bricks of such structures. Glass-ceramics are nanocomposite systems that exhibit specific morphologic, structural and spectroscopic properties allowing developing new physical concepts, for instance the mechanism related to the transparency, as well as novel photonic devices based on the enhancement of the luminescence. The dependence of the final product on the specific parent glass and on the fabrication protocol still remain an important task of the research in material science. Looking to application, the enhanced spectroscopic properties typical of glass ceramic in respect to those of the amorphous structures constitute an important point for the development of integrated optics devices, including optical amplifiers, monolithic waveguide laser, novel sensors, coating of spherical microresonators, and up and down converters. This paper presents some results obtained by our consortium regarding glass-based photonics systems. We will comment the energy transfer mechanism in transparent glass ceramics taking as examples the up and down conversion systems and the role of SnO2 nanocrystals as sensitizers. Coating of spherical resonators by glass ceramics, 1D-Photonic Crystals for luminescence enhancement, laser action and disordered 1-D photonic structures will be also discussed. Finally, RF-Sputtered rare earth doped P2O5- SiO2-Al2O3-Na2O-Er2O3 planar waveguides, will be presented.

  17. Inverse design of disordered stealthy hyperuniform spin chains

    Science.gov (United States)

    Chertkov, Eli; DiStasio, Robert A.; Zhang, Ge; Car, Roberto; Torquato, Salvatore

    2016-02-01

    Positioned between crystalline solids and liquids, disordered many-particle systems which are stealthy and hyperuniform represent new states of matter that are endowed with novel physical and thermodynamic properties. Such stealthy and hyperuniform states are unique in that they are transparent to radiation for a range of wave numbers around the origin. In this work, we employ recently developed inverse statistical-mechanical methods, which seek to obtain the optimal set of interactions that will spontaneously produce a targeted structure or configuration as a unique ground state, to investigate the spin-spin interaction potentials required to stabilize disordered stealthy hyperuniform one-dimensional (1D) Ising-type spin chains. By performing an exhaustive search over the spin configurations that can be enumerated on periodic 1D integer lattices containing N =2 ,3 ,...,36 sites, we were able to identify and structurally characterize all stealthy hyperuniform spin chains in this range of system sizes. Within this pool of stealthy hyperuniform spin configurations, we then utilized such inverse optimization techniques to demonstrate that stealthy hyperuniform spin chains can be realized as either unique or degenerate disordered ground states of radial long-ranged (relative to the spin-chain length) spin-spin interactions. Such exotic ground states appear to be distinctly different from spin glasses in both their inherent structural properties and the nature of the spin-spin interactions required to stabilize them. As such, the implications and significance of the existence of these disordered stealthy hyperuniform ground-state spin systems warrants further study, including whether their bulk physical properties and excited states, like their many-particle system counterparts, are singularly remarkable, and can be experimentally realized.

  18. Decoherence dynamics of a single spin versus spin ensemble

    NARCIS (Netherlands)

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

    2008-01-01

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

  19. Decoherence dynamics of a single spin versus spin ensemble

    NARCIS (Netherlands)

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

    2008-01-01

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

  20. Random spin freezing in uranium intermetallic compound UCuSi

    Energy Technology Data Exchange (ETDEWEB)

    Li Dexin [Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Nimori, Shigeki [Tsukuba Magnet Laboratory, National Institute for Materials Science, 3-13 Sakura, Tsukuba 305-0003 (Japan); Shiokawa, Yoshinobu [Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan)

    2006-03-29

    The results of low-temperature ac susceptibility, dc magnetization, magnetic relaxation, specific heat, and electrical resistivity measurements on the uranium intermetallic compound UCuSi, a hexagonal CeCd{sub 2}-type non-magnetic atom disorder system, are reported. The results establish that a spin-glass state is formed in this compound at low temperature. Some dynamical parameters characterizing the spin freezing state of this system, such as static spin freezing temperature T{sub s}, critical exponent z{nu}, and activation energy E{sub a}, are determined from dynamical analysis of the ac susceptibility data. The observed properties are discussed based on a magnetic cluster model.

  1. A Quantum Spin System with Random Interactions I

    Indian Academy of Sciences (India)

    Stephen Dias Barreto

    2000-11-01

    We study a quantum spin glass as a quantum spin system with random interactions and establish the existence of a family of evolution groups $\\{\\mathcal{T}_t()\\}_{\\in}$ of the spin system. The notion of ergodicity of a measure preserving group of automorphisms of the probability space , is used to prove the almost sure independence of the Arveson spectrum $\\mathrm{Sp}(\\mathcal{T}())$ of $\\mathcal{T}_t()$. As a consequence, for any family of $(\\mathcal{T}(), )$-KMS states {ρ()}, the spectrum of the generator of the group of unitaries which implement $\\mathcal{T}()$ in the GNS representation is also almost surely independent of .

  2. Spin-polarized spin excitation spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Loth, Sebastian; Lutz, Christopher P; Heinrich, Andreas J, E-mail: lothseb@us.ibm.com, E-mail: heinrich@almaden.ibm.com [IBM Research Division, Almaden Research Center, San Jose, CA 95120 (United States)

    2010-12-15

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

  3. Magnons, Spin Current and Spin Seebeck Effect

    Science.gov (United States)

    Maekawa, Sadamichi

    2012-02-01

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

  4. Entangled spins and ghost-spins

    CERN Document Server

    Jatkar, Dileep P

    2016-01-01

    We study patterns of quantum entanglement in systems of spins and ghost-spins regarding them as simple quantum mechanical toy models for theories containing negative norm states. We define a single ghost-spin as in arXiv:1602.06505 [hep-th] as a 2-state spin variable with an indefinite inner product in the state space. We find that whenever the spin sector is disentangled from the ghost-spin sector (both of which could be entangled within themselves), the reduced density matrix obtained by tracing over all the ghost-spins gives rise to positive entanglement entropy for positive norm states, while negative norm states have an entanglement entropy with a negative real part and a constant imaginary part. However when the spins are entangled with the ghost-spins, there are new entanglement patterns in general. For systems where the number of ghost-spins is even, it is possible to find subsectors of the Hilbert space where positive norm states always lead to positive entanglement entropy after tracing over the gho...

  5. Liquid Glass: A Facile Soft Replication Method for Structuring Glass.

    Science.gov (United States)

    Kotz, Frederik; Plewa, Klaus; Bauer, Werner; Schneider, Norbert; Keller, Nico; Nargang, Tobias; Helmer, Dorothea; Sachsenheimer, Kai; Schäfer, Michael; Worgull, Matthias; Greiner, Christian; Richter, Christiane; Rapp, Bastian E

    2016-06-01

    Liquid glass is a photocurable amorphous silica nanocomposite that can be structured using soft replication molds and turned into glass via thermal debinding and sintering. Simple polymer bonding techniques allow the fabrication of complex microsystems in glass like microfluidic chips. Liquid glass is a step toward prototyping of glass microstructures at low cost without requiring cleanroom facilities or hazardous chemicals.

  6. Mechanically reinforced glass beams

    DEFF Research Database (Denmark)

    Nielsen, Jens Henrik; Olesen, John Forbes

    2007-01-01

    The use of glass as a load carrying material in structural elements is rarely seen even though glass is a popular material for many architects. This is owed to the unreliable and low tensile strength, which is due to surface flaws and high brittleness of the material. These properties lead...... to breakage without any warning or ductility, which can be catastrophic if no precautions are taken. One aspect of this issue is treated here by looking at the possibility of mechanically reinforcing glass beams in order to obtain ductile failure for such a structural component. A mechanically reinforced...... laminated float glass beam is constructed and tested in four-point bending. The beam consist of 4 layers of glass laminated together with a slack steel band glued onto the bottom face of the beam. The glass parts of the tested beams are \\SI{1700}{mm} long and \\SI{100}{mm} high, and the total width of one...

  7. Radiation effects in glasses

    Energy Technology Data Exchange (ETDEWEB)

    Ehrt, D.; Vogel, W. (Otto-Schott-Inst., Chemische Fakultaet, Friedrich-Schiller-Univ., Jena (Germany))

    1992-03-01

    Glass was produced by man about 4000 years ago. The scientific exploration of glass is very young and closely connected with Jena. Fraunhofer, Goethe, Dobereiner, Abbe, Zeiss and Schott are famous names on this field. Both crystals and glasses are solids. However, there are fundamental differences in their properties and behavior. Glass is a thermodynamically unstable state and has a defect structure compared to the crystal. Glass and its properties are subject to a variety of changes under the influence of high energy radiation. In general, effects extend from the reduction of specific ions to the collapse of the entire network. Ultraviolet and X-ray radiation effects on UV-transmitting glasses will be discussed. (orig.).

  8. Homogeneity of Inorganic Glasses

    DEFF Research Database (Denmark)

    Jensen, Martin; Zhang, L.; Keding, Ralf;

    2011-01-01

    Homogeneity of glasses is a key factor determining their physical and chemical properties and overall quality. However, quantification of the homogeneity of a variety of glasses is still a challenge for glass scientists and technologists. Here, we show a simple approach by which the homogeneity...... of different glass products can be quantified and ranked. This approach is based on determination of both the optical intensity and dimension of the striations in glasses. These two characteristic values areobtained using the image processing method established recently. The logarithmic ratio between...... the dimension and the intensity is used to quantify and rank the homogeneity of glass products. Compared with the refractive index method, the image processing method has a wider detection range and a lower statistical uncertainty....

  9. Homogeneity of Inorganic Glasses

    DEFF Research Database (Denmark)

    Jensen, Martin; Zhang, L.; Keding, Ralf

    2011-01-01

    Homogeneity of glasses is a key factor determining their physical and chemical properties and overall quality. However, quantification of the homogeneity of a variety of glasses is still a challenge for glass scientists and technologists. Here, we show a simple approach by which the homogeneity...... of different glass products can be quantified and ranked. This approach is based on determination of both the optical intensity and dimension of the striations in glasses. These two characteristic values areobtained using the image processing method established recently. The logarithmic ratio between...... the dimension and the intensity is used to quantify and rank the homogeneity of glass products. Compared with the refractive index method, the image processing method has a wider detection range and a lower statistical uncertainty....

  10. Raman Spectra of Glasses

    Science.gov (United States)

    1986-11-30

    17), Raman spectra, plus a , . theoretical treatment of the data, f complex fluorozirconate 14 I anions in ZBLAN glasses and melts (16), and...based ZBLAN glasses ) 17. ICORS (International Conference on Raman Spectroscopy) Proceedings, London, England. Conferencf 5-9 Sep 88. (Molten silica...RESEARCH FINAL REPORT DTIC CONTRACT N00014-81-K-0501 &JELECTE 1 MAY 81 -- 30 NOV 86 EJJAN041989 V "RAMAN SPECTRA OF GLASSES " 0 During the five years of the

  11. Diamond turning of glass

    Energy Technology Data Exchange (ETDEWEB)

    Blackley, W.S.; Scattergood, R.O.

    1988-12-01

    A new research initiative will be undertaken to investigate the critical cutting depth concepts for single point diamond turning of brittle, amorphous materials. Inorganic glasses and a brittle, thermoset polymer (organic glass) are the principal candidate materials. Interrupted cutting tests similar to those done in earlier research are Ge and Si crystals will be made to obtain critical depth values as a function of machining parameters. The results will provide systematic data with which to assess machining performance on glasses and amorphous materials

  12. Metal Halide Optical Glasses.

    Science.gov (United States)

    1988-01-01

    while some of the multi- component "modified" glasses (e.g., ZBLAN ) could easily be cast into pieces several mm thick. 23 The difference between the...energy. 7-1 0 Typical plots pf 24 of log Iqi versus ]/Tf for ZB-I, ZBL, ZBLA, ZBLAN and ZBLALi glasses are presented in Fig. 3. These plots are linear... ZBLAN glasses are more resistant to devitrification than the corresponding ZBLLi or ZBLN glasses , although this does not appear to be manifested in

  13. Spin Rotation of Formalism for Spin Tracking

    Energy Technology Data Exchange (ETDEWEB)

    Luccio,A.

    2008-02-01

    The problem of which coefficients are adequate to correctly represent the spin rotation in vector spin tracking for polarized proton and deuteron beams in synchrotrons is here re-examined in the light of recent discussions. The main aim of this note is to show where some previous erroneous results originated and how to code spin rotation in a tracking code. Some analysis of a recent experiment is presented that confirm the correctness of the assumptions.

  14. Paleomagnetism of Lonar Crater Impact Glass

    Science.gov (United States)

    Garrick-Bethell, I.; Weiss, B. P.; Maloof, A. C.; Stewart, S. T.; Louzada, K. L.; Soule, S. A.; Swanson-Hysell, N.

    2006-12-01

    The source of magnetic fields on extraterrestrial bodies is largely unknown. There is particularly little information about magnetic fields on asteroids and the Moon for the last 3 billion years because most samples from these bodies predate this time. An exception is the small amount of impact-melt which has been continuously created by hypervelocity impactors over most of solar system history. Impact melt can be used to test the controversial hypothesis that magnetic fields on extraterrestrial bodies were predominantly the product of impact-produced plasmas rather than of core dynamos. However, to date only a small amount of impact melt has been analyzed paleomagnetically. To assess the quality of impact melts as recorders of magnetic fields, in January 2004 and January 2005 we collected thousands of samples of basaltic glass from the perimeter of Lonar Crater, a 1.8 km diameter impact crater which formed approximately 50,000 years ago in the Deccan Traps in Maharashtra, India. Lonar crater is a unique extraterrestrial analog because it is the only fresh impact crater on the Earth in a basaltic target. Most glass samples have rounded features and are between 0.01 and 1 cm in size, indicating that they are fladen and impact spherules (microtektites) formed from molten ejecta that cooled in mid-air while subject to rotational and aerodynamic forces. We have found that both types of glasses are strongly magnetic (saturation remanence of ~2 A m-1), contain ferromagnetic crystals that are predominantly single domain in size, and have no significant remanence anisotropy. The glasses also carry a natural remanent magnetization (NRM) presumably acquired just after the impact. However, alternating field demagnetization results in large directional changes of the magnetic moment, with little decrease in moment intensity. We interpret this unusual behavior as progressive removal of different coercivity components that cooled while the orientation of the spinning glasses

  15. Real space renormalization group theory of disordered models of glasses.

    Science.gov (United States)

    Angelini, Maria Chiara; Biroli, Giulio

    2017-03-28

    We develop a real space renormalization group analysis of disordered models of glasses, in particular of the spin models at the origin of the random first-order transition theory. We find three fixed points, respectively, associated with the liquid state, with the critical behavior, and with the glass state. The latter two are zero-temperature ones; this provides a natural explanation of the growth of effective activation energy scale and the concomitant huge increase of relaxation time approaching the glass transition. The lower critical dimension depends on the nature of the interacting degrees of freedom and is higher than three for all models. This does not prevent 3D systems from being glassy. Indeed, we find that their renormalization group flow is affected by the fixed points existing in higher dimension and in consequence is nontrivial. Within our theoretical framework, the glass transition results in an avoided phase transition.

  16. Observation of/β-Relaxation in Sub-Tg Isothermally Annealed A1-Based Metallic Glasses

    Institute of Scientific and Technical Information of China (English)

    YANG Hong-Wang; TONG Wei-Ping; ZHAO Xiang; ZUO Liang; WANG Jian-Qiang

    2008-01-01

    AlssNi5 Y8 Co2 and Al85Ni5 Y6 Co2Fe2 metallic glasses are fabricated by melt spinning. A kink or a small exothermic peak is observed for both the samples isothermally annealed at sub-glass transition temperatures. Temperature modulated differential scanning calorimetry (TMDSC) data disapprove amorphous phase separation. The activation energies derived from Kissinger plots of the exothermic process on DSC curve around glass transition temperature are consistent with those of β-relaxation of metallic glasses.

  17. Spin-Mechatronics

    Science.gov (United States)

    Matsuo, Mamoru; Saitoh, Eiji; Maekawa, Sadamichi

    2017-01-01

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

  18. Lanthanoides in Glass and Glass Ceramics

    Science.gov (United States)

    Meinhardt, Jürgen; Kilo, Martin; Somorowsky, Ferdinand; Hopp, Werner

    2017-03-01

    Many types of glass contain lanthanoides; among them, special glass for optical applications is the one with the highest content of lanthanoides. The precise determination of the lanthanoides' concentration is performed by inductively coupled plasma-optical emission spectrometry (ICP-OES). However, up to now, there are no established standard processes guaranteeing a uniform approach to the lanthanoide analysis. The knowledge of the lanthanoides' concentrations is necessary on the microscale in some cases, especially if a suitable separation and recycling procedure is to be applied. Here, the analysis is performed by energy-dispersive X-ray (EDX) or wavelength-dispersive X-ray (WDX) analytics in the scanning electron microscope.

  19. Spin relaxation in geometrically frustrated pyrochlores

    Science.gov (United States)

    Dunsiger, Sarah Ruth

    This thesis describes muSR experiments which focus on systems where the magnetic ions occupy the vertices of edge or corner sharing triangular units, in particular the pyrochlores A2B2O7. The scientific interest in pyrochlores is based on the fact that they display novel magnetic behaviour at low temperatures due to geometrical frustration. The ground state of these systems is sensitively dependent on such factors as the range of the spin-spin interactions, disorder, anisotropy, thermal and quantum fluctuations. For example, Y2Mo2O7 shows many features reminiscent of a conventional spin glass, even though this material has nominally zero chemical disorder. It is found that the muon spin polarisation obeys a time-field scaling relation which indicates that the spin-spin autocorrelation function has a power law form in time, in stark contrast with the exponential form often assumed for conventional magnets above their transition temperature. Gd2Ti2O7 shows long range order, but only at a temperature much lower than its Curie-Weiss temperature, a signature of a frustrated system. In the paramagnetic regime, it is well described by an isotropic Heisenberg Hamiltonian with nearest neighbour couplings in the presence of a Zeeman interaction, from which the spin-spin autocorrelation function may be calculated as a power series in time. The muon spin relaxation rate decreases with magnetic field as the Zeeman energy becomes comparable with the exchange coupling between Gd spins. Thus, an independent measure of the exchange coupling or equivalently the Gd spin fluctuation rate is extracted. By contrast, Tb2Ti2O7 has been identified as a type of cooperative paramagnet. Short range correlations develop below 50 K. However, there is no long range ordering down to very low temperatures (0.075 K). The Tb3+ ion is subject to strong crystal electric field effects: point charge calculations indicate that this system is Ising like at low temperatures. Thus this system may be

  20. Electric glass capturing markets

    Energy Technology Data Exchange (ETDEWEB)

    Wikman, K.; Wikstroem, T.

    1996-11-01

    Electric glass has found its place on the construction market. In public buildings, electrically heatable windows are becoming the leading option for large glass walls. Studies on detached houses, both new and renovated, show that floor heating combined with electrically heatable windowpanes is the best choice with respect to resident`s comfort. (orig.)

  1. lead glass brick

    CERN Multimedia

    As well as accelerators to boost particles up to high energy, physicists need detectors to see what happens when those particles collide. This lead glass block is part of a CERN detector called OPAL. OPAL uses some 12 000 blocks of glass like this to measure particle energies.

  2. Glasses for photonic applications

    NARCIS (Netherlands)

    Richardson, K.; Krol, D.M.; Hirao, K.

    2010-01-01

    Recent advances in the application of glassy materials in planar and fiber-based photonic structures have led to novel devices and components that go beyond the original thinking of the use of glass in the 1960s, when glass fibers were developed for low-loss, optical communication applications. Expl

  3. Getting Started with Glass

    Science.gov (United States)

    White, Heather

    2007-01-01

    The metamorphosis of glass when heated is a magical process to students, yet teachers are often reluctant to try it in class. The biggest challenge in working with glass in the classroom is to simplify procedures just enough to ensure student success while maintaining strict safety practices so no students are injured. Project concepts and safety…

  4. Glass Sword of Damocles

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    A string of accidents draws attention to the safety of the gleaming glass-walled skyscrapers, now common in China’s major cities On July 8, as 19-year-old Zhu Yiyi was walking past a 23-story building in Hangzhou, east China’s Zhejiang Province, shards of glass falling

  5. Electric glass capturing markets

    Energy Technology Data Exchange (ETDEWEB)

    Wikman, K.; Wikstroem, T.

    1996-11-01

    Electric glass has found its place on the construction market. In public buildings, electrically heatable windows are becoming the leading option for large glass walls. Studies on detached houses, both new and renovated, show that floor heating combined with electrically heatable windowpanes is the best choice with respect to resident`s comfort. (orig.)

  6. Spin Transport by Collective Spin Excitations

    Science.gov (United States)

    Hammel, P. Chris

    We report studies of angular momentum transport in insulating materials. Our measurements reveal efficient spin pumping from high wavevector k spin waves in thin film Y3Fe5O12 (YIG): spin pumping is independent of wavevector up to k ~ 20 μm-1. Optical detection of YIG FMR by NV centers in diamond reveals a role for spin waves in this insulator-to-insulator spin transfer process. Spin transport is typically suppressed by insulating barriers, but we find that fluctuating antiferromagnetic correlations enable efficient spin transport at nm-scale thicknesses in insulating antiferromagnets, even in the absence of long-range order, and that the spin decay length increases with the strength of the antiferromagnetic correlations. This research is supported by the U.S. DOE through Grants DE-FG02-03ER46054 and DE-SC0001304, by the NSF MRSEC program through Grant No. 1420451 and by the Army Research Office through Grant W911NF0910147.

  7. Dynamic nuclear spin polarization

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-11-01

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

  8. Higher spin black holes

    National Research Council Canada - National Science Library

    Gutperle, Michael; Kraus, Per

    2011-01-01

    .... 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...

  9. Arbitrary Spin Galilean Oscillator

    CERN Document Server

    Hagen, C R

    2014-01-01

    The so-called Dirac oscillator was proposed as a modification of the free Dirac equation which reproduces many of the properties of the simple harmonic oscillator but accompanied by a strong spin-orbit coupling term. It has yet to be extended successfully to the arbitrary spin S case primarily because of the unwieldiness of general spin Lorentz invariant wave equations. It is shown here using the formalism of totally symmetric multispinors that the Dirac oscillator can, however, be made to accommodate spin by incorporating it into the framework of Galilean relativity. This is done explicitly for spin zero and spin one as special cases of the arbitrary spin result. For the general case it is shown that the coefficient of the spin-orbit term has a 1/S behavior by techniques which are virtually identical to those employed in the derivation of the g-factor carried out over four decades ago.

  10. Defense HLW Glass Degradation Model

    Energy Technology Data Exchange (ETDEWEB)

    D. Strachan

    2004-10-20

    The purpose of this report is to document the development of a model for calculating the release rate for radionuclides and other key elements from high-level radioactive waste (HLW) glasses under exposure conditions relevant to the performance of the repository. Several glass compositions are planned for the repository, some of which have yet to be identified (i.e., glasses from Hanford and Idaho National Engineering and Environmental Laboratory). The mechanism for glass dissolution is the same for these glasses and the glasses yet to be developed for the disposal of DOE wastes. All of these glasses will be of a quality consistent with the glasses used to develop this report.

  11. Spinning Eggs and Ballerinas

    Science.gov (United States)

    Cross, Rod

    2013-01-01

    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. Spinning Eggs and Ballerinas

    Science.gov (United States)

    Cross, Rod

    2013-01-01

    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…

  13. Thermal Conductivity of Foam Glass

    DEFF Research Database (Denmark)

    Petersen, Rasmus Rosenlund; König, Jakob; Yue, Yuanzheng

    Due to the increased focus on energy savings and waste recycling foam glass materials have gained increased attention. The production process of foam glass is a potential low-cost recycle option for challenging waste, e.g. CRT glass and industrial waste (fly ash and slags). Foam glass is used...... as thermal insulating material in building and chemical industry. The large volume of gas (porosity 90 – 95%) is the main reason of the low thermal conductivity of the foam glass. If gases with lower thermal conductivity compared to air are entrapped in the glass melt, the derived foam glass will contain...... only closed pores and its overall thermal conductivity will be much lower than that of the foam glass with open pores. In this work we have prepared foam glass using different types of recycled glasses and different kinds of foaming agents. This enabled the formation of foam glasses having gas cells...

  14. Bioactive glasses and glass-ceramics

    Directory of Open Access Journals (Sweden)

    de Aza, P. N.

    2007-04-01

    Full Text Available Since the late 1960´s, a great interest in the use of bioceramic materials for biomedical applications has been developed. In a previous paper, the authors reviewed crystalline bioceramic materials “sensus stricto”, it is to say, those ceramic materials, constituted for non-metallic inorganic compounds, crystallines and consolidates by thermal treatment of powders at high temperature. In the present review, the authors deal with those called bioactive glasses and glassceramics. Although all of them are also obtained by thermal treatment at high temperature, the first are amorphous and the second are obtained by devitrification of a glass, although the vitreous phase normally prevails on the crystalline phases. After an introduction to the concept of bioactive materials, a short historical review of the bioactive glasses development is made. Its preparation, reactivity in physiological media, mechanism of bonding to living tissues and mechanical strength of the bone-implant interface is also reported. Next, the concept of glass-ceramic and the way of its preparation are exposed. The composition, physicochemical properties and biological behaviour of the principal types of bioactive glasses and glass-ceramic materials: Bioglass®, Ceravital®, Cerabone®, Ilmaplant® and Bioverit® are also reviewed. Finally, a short review on the bioactive-glass coatings and bioactive-composites and most common uses of bioactive-glasses and glass-ceramics are carried out too.

    Desde finales de los años sesenta, se ha despertado un gran interés por el uso de los materiales biocerámicos para aplicaciones biomédicas. En un trabajo previo, los autores hicieron una revisión de los denominados materiales biocerámicos cristalinos en sentido estricto, es decir, de aquellos materiales, constituidos por compuestos inorgánicos no metálicos, cristalinos y consolidados mediante tratamientos térmicos a altas temperaturas. En el presente trabajo, los autores

  15. Ising Spin Glass:. Recent Progress in the Field Theory Approach

    Science.gov (United States)

    Dominicis, C. De; Kondor, I.; Temesvari, T.

    A loop expansion around Parisi's replica symmetry breaking mean field theory is constructed, in zero field. We obtain the equation of state (and associated Parisi's solution) below the upper critical dimension du=6, and, in particular, explicit corrections in ɛlnt and (ɛlnt)2 with t=(Tc-T)/Tc and ɛ=6-d. This allows us to verify that standard scaling is satisfied with β=1+ɛ/2+0(ɛ2). We have also investigated the transverse (replicon) correlation function, particularly at zero overlap. Near du, G00 (p) ~ t/P4 (for p~0) is the most obvious obstacle to a meaningful theory in d=3. If we make the twofold assumption that (i) scaling applies, and (ii) the replicon propagator is dominated by the spectrum of the (small) transverse masses, we obtain the softer behavior G00(p) ~ (1/p2-η). (t/p1/v)β and a prediction for a soft replicon spectrum in tγk2γ/β γ/β instead of tk2 at du. We have checked tγ to one loop and work is in progress to check k2γ/β to the same order. Taking the above divergence in p-(d+2-η)/2 as the leading divergence defines the lower critical dimension d ℓ by d ℓ=2-η (d ℓ). Known values of η (at d=6, from the ɛ expansion at Tc, or from numerical work at d=4, 3) are compatible with d ℓ ~ 2.5±.3.

  16. Correlation Inequalities for Spin Glass in one Dimension

    CERN Document Server

    Contucci, Pierluigi

    2007-01-01

    We prove two inequalities for the direct and truncated correlation for the nearest-neighboor one-dimensional Edwards-Anderson model with symmetric quenched disorder. The second inequality has the opposite sign of the GKS inequality of type II. In the non symmetric case with positive average we show that while the direct correlation keeps its sign the truncated one changes sign when crossing a suitable line in the parameter space. That line separates the regions satisfying the GKS second inequality and the one proved here.

  17. Quenched disorder and spin-glass correlations in XY nematics

    Energy Technology Data Exchange (ETDEWEB)

    Petridis, L; Terentjev, E M [Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE (United Kingdom)

    2006-08-04

    We present a theoretical study of the equilibrium ordering in a 3D XY nematic system with quenched random disorder. Within this model, treated with the replica trick and Gaussian variational method, the correlation length is obtained as a function of the local nematic order parameter Q and the effective disorder strength {gamma}. These results, {xi} {approx} Q{sup 2}e{sup 1/Q{sup 2}} and {xi} {approx} (1/{gamma}) e{sup -{gamma}}, clarify what happens in the limiting cases of diminishing Q and {gamma}, that is near a phase transition of a pure system. In particular, it is found that quenched disorder is irrelevant as Q {yields} 0 and hence does not change the character of the continuous XY nematic-isotropic phase transition. We discuss how these results compare with experiments and simulations.

  18. Spin glasses and nonlinear constraints in portfolio optimization

    Energy Technology Data Exchange (ETDEWEB)

    Andrecut, M., E-mail: mircea.andrecut@gmail.com

    2014-01-17

    We discuss the portfolio optimization problem with the obligatory deposits constraint. Recently it has been shown that as a consequence of this nonlinear constraint, the solution consists of an exponentially large number of optimal portfolios, completely different from each other, and extremely sensitive to any changes in the input parameters of the problem, making the concept of rational decision making questionable. Here we reformulate the problem using a quadratic obligatory deposits constraint, and we show that from the physics point of view, finding an optimal portfolio amounts to calculating the mean-field magnetizations of a random Ising model with the constraint of a constant magnetization norm. We show that the model reduces to an eigenproblem, with 2N solutions, where N is the number of assets defining the portfolio. Also, in order to illustrate our results, we present a detailed numerical example of a portfolio of several risky common stocks traded on the Nasdaq Market.

  19. Spin glasses and nonlinear constraints in portfolio optimization

    Science.gov (United States)

    Andrecut, M.

    2014-01-01

    We discuss the portfolio optimization problem with the obligatory deposits constraint. Recently it has been shown that as a consequence of this nonlinear constraint, the solution consists of an exponentially large number of optimal portfolios, completely different from each other, and extremely sensitive to any changes in the input parameters of the problem, making the concept of rational decision making questionable. Here we reformulate the problem using a quadratic obligatory deposits constraint, and we show that from the physics point of view, finding an optimal portfolio amounts to calculating the mean-field magnetizations of a random Ising model with the constraint of a constant magnetization norm. We show that the model reduces to an eigenproblem, with 2N solutions, where N is the number of assets defining the portfolio. Also, in order to illustrate our results, we present a detailed numerical example of a portfolio of several risky common stocks traded on the Nasdaq Market.

  20. Environmental effects on electron spin relaxation in N@C60

    CERN Document Server

    Morton, J J L; Ardavan, A; Porfyrakis, K; Lyon, S A; Briggs, G A D; Morton, John J. L.; Tyryshkin, Alexei M.; Ardavan, Arzhang; Porfyrakis, Kyriakos

    2006-01-01

    We examine environmental effects of surrounding nuclear spins on the electron spin relaxation of the N@C60 molecule (which consists of a nitrogen atom at the centre of a fullerene cage). Using dilute solutions of N@C60 in regular and deuterated toluene, we observe and model the effect of translational diffusion of nuclear spins of the solvent molecules on the N@C60 electron spin relaxation times. We also study spin relaxation in frozen solutions of N@C60 in CS2, to which small quantities of a glassing agent, S2Cl2 are added. At low temperatures, spin relaxation is caused by spectral diffusion of surrounding nuclear (35,37)Cl spins in the S2Cl2, but nevertheless, at 20 K, T2 times as long as 0.23 ms are observed

  1. Evolution of magnetism in Ru doped Na2IrO3

    Science.gov (United States)

    Mehlawat, Kavita; Singh, Yogesh

    2016-05-01

    We synthesized Ru doped single crystalline samples of the honeycomb iridate material Na2IrO3 and studied their magnetic properties using AC and DC magnetic susceptibility. The parent compound Na2IrO3 is a spin orbit driven Mott insulator with long range order below TN = 15 K. We find that even smallest substitution of Ru changes the antiferromagnetic long range order state to a spin glass like state indicating the fragile nature of magnetism in Na2IrO3. We track the freezing temperature Tg as a function of Ru concentration and the shift of Tg with frequency f of the ac modulation in AC susceptibility which is found to be very different from canonical spin-glasses like Cu-Mn.

  2. Inverse spin Hall effect by spin injection

    Science.gov (United States)

    Liu, S. Y.; Horing, Norman J. M.; Lei, X. L.

    2007-09-01

    Motivated by a recent experiment [S. O. Valenzuela and M. Tinkham, Nature (London) 442, 176 (2006)], the authors present a quantitative microscopic theory to investigate the inverse spin-Hall effect with spin injection into aluminum considering both intrinsic and extrinsic spin-orbit couplings using the orthogonalized-plane-wave method. Their theoretical results are in good agreement with the experimental data. It is also clear that the magnitude of the anomalous Hall resistivity is mainly due to contributions from extrinsic skew scattering.

  3. Spin supplementary conditions for spinning compact binaries

    CERN Document Server

    Mikóczi, Balázs

    2016-01-01

    We consider the different spin supplementary conditions (SSC) for a spinning compact binary with the leading-order spin-orbit (SO) interaction. The Lagrangian of the binary system can be constructed but it is acceleration-dependent in two cases of SSC. We rewrite the generalized Hamiltonian formalism proposed by Ostrogradsky and compute the conservative quantities and the dissipative part of relative motion during the gravitational radiation of each SSCs. We give the orbital elements and observed quantities of the SO dynamics, for instance the energy and the orbital angular momentum losses and waveforms and discuss their SSC dependence.

  4. Kagome spin ice

    Science.gov (United States)

    Mellado, Paula

    Spin ice in magnetic pyrochlore oxides is a peculiar magnetic state. Like ordinary water ice, these materials are in apparent violation with the third law of thermodynamics, which dictates that the entropy of a system in thermal equilibrium vanishes as its temperature approaches absolute zero. In ice, a "zero-point" entropy is retained down to low temperatures thanks to a high number of low-energy positions of hydrogen ions associated with the Bernal-Fowler ice-rules. Spins in pyrochlore oxides Ho2Ti 2O7 and Dy2Ti2O7 exhibit a similar degeneracy of ground states and thus also have a sizable zero-point entropy. A recent discovery of excitations carrying magnetic charges in pyrochlore spin ice adds another interesting dimension to these magnets. This thesis is devoted to a theoretical study of a two-dimensional version of spin ice whose spins reside on kagome, a lattice of corner-sharing triangles. It covers two aspects of this frustrated classical spin system: the dynamics of artificial spin ice in a network of magnetic nanowires and the thermodynamics of crystalline spin ice. Magnetization dynamics in artificial spin ice is mediated by the emission, propagation and absorption of domain walls in magnetic nanowires. The dynamics shows signs of self-organized behavior such as avalanches. The theoretical model compares favorably to recent experiments. The thermodynamics of the microscopic version of spin ice on kagome is examined through analytical calculations and numerical simulations. The results show that, in addition to the high-temperature paramagnetic phase and the low-temperature phase with magnetic order, spin ice on kagome may have an intermediate phase with fluctuating spins and ordered magnetic charges. This work is concluded with a calculation of the entropy of kagome spin ice at zero temperature when one of the sublattices is pinned by an applied magnetic field and the system breaks up into independent spin chains, a case of dimensional reduction.

  5. Shattering the Glass Ceiling

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    @@ "Shattering the Glass Ceiling: the Myths, Opportunities and Chal lenges of Women in Corporate China" was the theme of CEIBS'first Women in Management Forum held on December l 1 on the school's main campus in Shanghai.

  6. Glass Stronger than Steel

    Science.gov (United States)

    Yarris, Lynn

    2011-03-28

    A new type of damage-tolerant metallic glass, demonstrating a strength and toughness beyond that of steel or any other known material, has been developed and tested by a collaboration of researchers from Berkeley Lab and Caltech.

  7. Glass for Solar Concentrators

    Science.gov (United States)

    Bouquet, F. L.

    1984-01-01

    Report identifies four commercially available glasses as promising reflectors for solar concentrators. Have properties of high reflectance (80 to 96 percent), lower cost than first-surface silver metalization, and resistance to environmental forces.

  8. Mechanically reinforced glass beams

    DEFF Research Database (Denmark)

    Nielsen, Jens Henrik; Olesen, John Forbes

    2007-01-01

    to breakage without any warning or ductility, which can be catastrophic if no precautions are taken. One aspect of this issue is treated here by looking at the possibility of mechanically reinforcing glass beams in order to obtain ductile failure for such a structural component. A mechanically reinforced...... the mechanical behavior of the beam is explained. Finally, some design criterions for reinforced glass beams are discussed....

  9. Baseline LAW Glass Formulation Testing

    Energy Technology Data Exchange (ETDEWEB)

    Kruger, Albert A. [USDOE Office of River Protection, Richland, WA (United States); Mooers, Cavin [The Catholic University of America, Washington, DC (United States). Vitreous State Lab.; Bazemore, Gina [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Pegg, Ian L. [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Hight, Kenneth [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Lai, Shan Tao [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Buechele, Andrew [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Rielley, Elizabeth [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Gan, Hao [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Muller, Isabelle S. [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Cecil, Richard [The Catholic University of America, Washington, DC (United States). Vitreous State Lab

    2013-06-13

    The major objective of the baseline glass formulation work was to develop and select glass formulations that are compliant with contractual and processing requirements for each of the LAW waste streams. Other objectives of the work included preparation and characterization of glasses with respect to the properties of interest, optimization of sulfate loading in the glasses, evaluation of ability to achieve waste loading limits, testing to demonstrate compatibility of glass melts with melter materials of construction, development of glass formulations to support ILAW qualification activities, and identification of glass formulation issues with respect to contract specifications and processing requirements.

  10. Slow spin relaxation in dipolar spin ice.

    Science.gov (United States)

    Orendac, Martin; Sedlakova, Lucia; Orendacova, Alzbeta; Vrabel, Peter; Feher, Alexander; Pajerowski, Daniel M.; Cohen, Justin D.; Meisel, Mark W.; Shirai, Masae; Bramwell, Steven T.

    2009-03-01

    Spin relaxation in dipolar spin ice Dy2Ti2O7 and Ho2Ti2O7 was investigated using the magnetocaloric effect and susceptibility. The magnetocaloric behavior of Dy2Ti2O7 at temperatures where the orientation of spins is governed by ``ice rules`` (T Tice) revealed thermally activated relaxation; however, the resulting temperature dependence of the relaxation time is more complicated than anticipated by a mere extrapolation of the corresponding high temperature data [1]. A susceptibility study of Ho2Ti2O7 was performed at T > Tice and in high magnetic fields, and the results suggest a slow relaxation of spins analogous to the behavior reported in a highly polarized cooperative paramagnet [2]. [1] J. Snyder et al., Phys. Rev. Lett. 91 (2003) 107201. [2] B. G. Ueland et al., Phys. Rev. Lett. 96 (2006) 027216.

  11. Spinning particles and higher spin field equations

    CERN Document Server

    Bastianelli, Fiorenzo; Corradini, Olindo; Latini, Emanuele

    2015-01-01

    Relativistic particles with higher spin can be described in first quantization using actions with local supersymmetry on the worldline. First, we present a brief review of these actions and their use in first quantization. In a Dirac quantization scheme the field equations emerge as Dirac constraints on the Hilbert space, and we outline how they lead to the description of higher spin fields in terms of the more standard Fronsdal-Labastida equations. Then, we describe how these actions can be extended so that the propagating particle is allowed to take different values of the spin, i.e. carry a reducible representation of the Poincar\\'e group. This way one may identify a four dimensional model that carries the same degrees of freedom of the minimal Vasiliev's interacting higher spin field theory. Extensions to massive particles and to propagation on (A)dS spaces are also briefly commented upon.

  12. Observation of the geometric spin Hall effect of light

    CERN Document Server

    Korger, Jan; Chille, Vanessa; Banzer, Peter; Wittmann, Christoffer; Lindlein, Norbert; Marquardt, Christoph; Leuchs, Gerd

    2013-01-01

    The spin Hall effect of light (SHEL) is the photonic analogue of spin Hall effects occurring for charge carriers in solid-state systems. A prime example of this intriguing phenomenon occurs when a light beam refracts at an air-glass interface. It amounts to a polarization-dependent displacement perpendicular to the plane of incidence. At optical wavelengths, this shift is about a few tens of nanometres. Recently, it was predicted that a light beam projected onto an oblique plane can undergo a significantly larger displacement. This effect, named geometric SHEL, is a consequence of spin-orbit coupling and is largely independent from the physical implementation of the projection. Here, we experimentally demonstrate this novel phenomenon by observing an optical beam transmitted across an oblique polarizer. The spatial intensity distribution of the transmitted beam depends on the incident state of polarization and its centroid undergoes a positional displacement exceeding one wavelength. This novel type of spin-o...

  13. Processing metallic glasses by selective laser melting

    Directory of Open Access Journals (Sweden)

    Simon Pauly

    2013-01-01

    Full Text Available Metallic glasses and their descendants, the so-called bulk metallic glasses (BMGs, can be regarded as frozen liquids with a high resistance to crystallization. The lack of a conventional structure turns them into a material exhibiting near-theoretical strength, low Young's modulus and large elasticity. These unique mechanical properties can be only obtained when the metallic melts are rapidly cooled to bypass the nucleation and growth of crystals. Most of the commonly known and used processing routes, such as casting, melt spinning or gas atomization, have intrinsic limitations regarding the complexity and dimensions of the geometries. Here, it is shown that selective laser melting (SLM, which is usually used to process conventional metallic alloys and polymers, can be applied to implement complex geometries and components from an Fe-base metallic glass. This approach is in principle viable for a large variety of metallic alloys and paves the way for the novel synthesis of materials and the development of parts with advanced functional and structural properties without limitations in size and intricacy.

  14. Wastes based glasses and glass-ceramics

    Directory of Open Access Journals (Sweden)

    Barbieri, L.

    2001-12-01

    Full Text Available Actually, the inertization, recovery and valorisation of the wastes coming from municipal and industrial processes are the most important goals from the environmental and economical point of view. An alternative technology capable to overcome the problem of the dishomogeneity of the raw material chemical composition is the vitrification process that is able to increase the homogeneity and the constancy of the chemical composition of the system and to modulate the properties in order to address the reutilization of the waste. Moreover, the glasses obtained subjected to different controlled thermal treatments, can be transformed in semy-cristalline material (named glass-ceramics with improved properties with respect to the parent amorphous materials. In this review the tailoring, preparation and characterization of glasses and glass-ceramics obtained starting from municipal incinerator grate ash, coal and steel fly ashes and glass cullet are described.

    Realmente la inertización, recuperación y valorización de residuos que proceden de los procesos de incineración de residuos municipales y de residuos industriales son metas importantes desde el punto de vista ambiental y económico. Una tecnología alternativa capaz de superar el problema de la heterogeneidad de la composición química de los materiales de partida es el proceso de la vitrificación que es capaz de aumentar la homogeneidad y la constancia de la composición química del sistema y modular las propiedades a fin de la reutilización del residuo. En este artículo se presentan los resultados de vitrificación en que los vidrios fueron sometidos a tratamientos térmicos controlados diferentes, de manera que se transforman en materiales semicristalinos (también denominados vitrocerámicos con mejores propiedades respecto a los materiales amorfos originales. En esta revisión se muestra el diseño, preparación y caracterización de vidrios y vitrocerámicos partiendo de

  15. Glass microsphere lubrication

    Science.gov (United States)

    Geiger, Michelle; Goode, Henry; Ohanlon, Sean; Pieloch, Stuart; Sorrells, Cindy; Willette, Chris

    1991-01-01

    The harsh lunar environment eliminated the consideration of most lubricants used on earth. Considering that the majority of the surface of the moon consists of sand, the elements that make up this mixture were analyzed. According to previous space missions, a large portion of the moon's surface is made up of fine grained crystalline rock, about 0.02 to 0.05 mm in size. These fine grained particles can be divided into four groups: lunar rock fragments, glasses, agglutinates (rock particles, crystals, or glasses), and fragments of meteorite material (rare). Analysis of the soil obtained from the missions has given chemical compositions of its materials. It is about 53 to 63 percent oxygen, 16 to 22 percent silicon, 10 to 16 percent sulfur, 5 to 9 percent aluminum, and has lesser amounts of magnesium, carbon, and sodium. To be self-supporting, the lubricant must utilize one or more of the above elements. Considering that the element must be easy to extract and readily manipulated, silicon or glass was the most logical choice. Being a ceramic, glass has a high strength and excellent resistance to temperature. The glass would also not contaminate the environment as it comes directly from it. If sand entered a bearing lubricated with grease, the lubricant would eventually fail and the shaft would bind, causing damage to the system. In a bearing lubricated with a solid glass lubricant, sand would be ground up and have little effect on the system. The next issue was what shape to form the glass in. Solid glass spheres was the only logical choice. The strength of the glass and its endurance would be optimal in this form. To behave as an effective lubricant, the diameter of the spheres would have to be very small, on the order of hundreds of microns or less. This would allow smaller clearances between the bearing and the shaft, and less material would be needed. The production of glass microspheres was divided into two parts, production and sorting. Production includes the

  16. Optimized Synthesis of Foam Glass from Recycled CRT Panel Glass

    DEFF Research Database (Denmark)

    Petersen, Rasmus Rosenlund; König, Jakob; Yue, Yuanzheng

    Most of the panel glass from cathode ray tubes (CRTs) is landfilled today. Instead of landfilling, the panel glass can be turned into new environment-friendly foam glass. Low density foam glass is an effective heat insulating material and can be produced just by using recycle glass and foaming...... additives. In this work we recycle the CRT panel glass to synthesize the foam glass as a crucial component of building and insulating materials. The synthesis conditions such as foaming temperature, duration, glass particle size, type and concentrations of foaming agents, and so on are optimized...... by performing systematic experiments. In particular, the concentration of foaming agents is an important parameter that influences the size of bubbles and the distribution of bubbles throughout the sample. The foam glasses are characterised regarding density and open/closed porosity. Differential scanning...

  17. DWPF GLASS BEADS AND GLASS FRIT TRANSPORT DEMONSTRATION

    Energy Technology Data Exchange (ETDEWEB)

    Adamson, D; Bradley Pickenheim, B

    2008-11-24

    DWPF is considering replacing irregularly shaped glass frit with spherical glass beads in the Slurry Mix Evaporator (SME) process to decrease the yield stress of the melter feed (a non-Newtonian Bingham Plastic). Pilot-scale testing was conducted on spherical glass beads and glass frit to determine how well the glass beads would transfer when compared to the glass frit. Process Engineering Development designed and constructed the test apparatus to aid in the understanding and impacts that spherical glass beads may have on the existing DWPF Frit Transfer System. Testing was conducted to determine if the lines would plug with the glass beads and the glass frit slurry and what is required to unplug the lines. The flow loop consisted of vertical and horizontal runs of clear PVC piping, similar in geometry to the existing system. Two different batches of glass slurry were tested: a batch of 50 wt% spherical glass beads and a batch of 50 wt% glass frit in process water. No chemicals such as formic acid was used in slurry, only water and glass formers. The glass beads used for this testing were commercially available borosilicate glass of mesh size -100+200. The glass frit was Frit 418 obtained from DWPF and is nominally -45+200 mesh. The spherical glass beads did not have a negative impact on the frit transfer system. The transferring of the spherical glass beads was much easier than the glass frit. It was difficult to create a plug with glass bead slurry in the pilot transfer system. When a small plug occurred from setting overnight with the spherical glass beads, the plug was easy to displace using only the pump. In the case of creating a man made plug in a vertical line, by filling the line with spherical glass beads and allowing the slurry to settle for days, the plug was easy to remove by using flush water. The glass frit proved to be much more difficult to transfer when compared to the spherical glass beads. The glass frit impacted the transfer system to the point

  18. Optical absorption and fluorescence properties of $Er^{3+}$ in sodium borate glass

    OpenAIRE

    Ratnakaram, YC; J.Lakshmi; Chakradhar, RPS

    2005-01-01

    Spectroscopic properties of $Er^{3+}$ ions in sodium borate glass have been studied. The indirect and direct optical band gaps $(E_{opt})$ and energy level parameters (Racah $(E^{1}, E^{2} and E^{3})$, spin-orbit $(\\xi_{4f})$ and configurational interaction (\\alpha)) are evaluated. Spectral intensities for various absorption bands of $Er^{3+}$ doped sodium borate glass are calculated. Using Judd-Ofelt intensity parameters $(\\Omega_{2},\\Omega_{4}, \\Omega_{6})$, radiative transition probabiliti...

  19. Effects of impurities and vortices on the low-energy spin excitations in high-Tc materials

    DEFF Research Database (Denmark)

    Andersen, Brian Møller; Graser, S.; Schmid, M.

    2011-01-01

    We review a theoretical scenario for the origin of the spin-glass phase of underdoped cuprate materials. In particular it is shown how disorder in a correlated d-wave superconductor generates a magnetic phase by inducing local droplets of antiferromagnetic order which eventually merge and form a ...... disorder and/or applied magnetic fields lead to a slowing down of the dynamical spin fluctuations in agreement with neutron scattering and muon spin rotation (mSR) experiments....

  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)

    2015-06-14

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

  1. Higher spin gauge theories

    CERN Document Server

    Henneaux, Marc; Vasiliev, Mikhail A

    2017-01-01

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

  2. Quantum Spin Gyroscope

    Science.gov (United States)

    2015-07-15

    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...required large volumes. Our project aims at overcoming these drawbacks by developing a novel solid-state quantum spin gyro- scope associated with the

  3. Spin coating apparatus

    Science.gov (United States)

    Torczynski, John R.

    2000-01-01

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

  4. Magnetic glass state and magnetoresistance in SrLaFeCoO6 double perovskite

    Science.gov (United States)

    Pradheesh, R.; Nair, Harikrishnan S.; Haripriya, G. R.; Senyshyn, Anatoliy; Chatterji, Tapan; Sankaranarayanan, V.; Sethupathi, K.

    2017-03-01

    Unusual features in magnetization resembling the kinetic arrest of a magnetic glass state are observed in the La-doped double perovskite, SrLaFeCoO6. Neutron powder diffraction experiments confirm the presence of antisite disorder as well as a lack of long-range magnetic order down to 4 K in this double perovskite which displays spin glass-like features in dc and ac susceptibilities. Magnetic relaxation observed through cooling and heating under unequal fields (CHUF) point towards unusual domain dynamics which is supported by a broad memory effect. Among the two anomalies that are observed at {{T}\\text{a1}}≈ 75 K and at {{T}\\text{a2}}≈ 250 K in the magnetic measurements, the former is associated with a spin-freezing temperature below which the magnetic glass state is experimentally verified. The magnetometric experiments detailed in the paper bring out the non-equilibrium metastable magnetic states in this disordered magnetic system. The magnetic glass state described above manifests in the electrical resistivity ρ (T) through the formation of a ‘hard gap’ because of the spin-exchange energy following the formation of magnetic glass. It is observed that the combination of disorder and magnetic glass state leads to a large, negative magnetoresistance (MR) of  ≈47 % at 5 K in 8 T.

  5. Spin jam induced by quantum fluctuations in a frustrated magnet.

    Science.gov (United States)

    Yang, Junjie; Samarakoon, Anjana; Dissanayake, Sachith; Ueda, Hiroaki; Klich, Israel; Iida, Kazuki; Pajerowski, Daniel; Butch, Nicholas P; Huang, Q; Copley, John R D; Lee, Seung-Hun

    2015-09-15

    Since the discovery of spin glasses in dilute magnetic systems, their study has been largely focused on understanding randomness and defects as the driving mechanism. The same paradigm has also been applied to explain glassy states found in dense frustrated systems. Recently, however, it has been theoretically suggested that different mechanisms, such as quantum fluctuations and topological features, may induce glassy states in defect-free spin systems, far from the conventional dilute limit. Here we report experimental evidence for existence of a glassy state, which we call a spin jam, in the vicinity of the clean limit of a frustrated magnet, which is insensitive to a low concentration of defects. We have studied the effect of impurities on SrCr9pGa12-9pO19 [SCGO(p)], a highly frustrated magnet, in which the magnetic Cr(3+) (s = 3/2) ions form a quasi-2D triangular system of bipyramids. Our experimental data show that as the nonmagnetic Ga(3+) impurity concentration is changed, there are two distinct phases of glassiness: an exotic glassy state, which we call a spin jam, for the high magnetic concentration region (p > 0.8) and a cluster spin glass for lower magnetic concentration (p jam is a unique vantage point from which the class of glassy states of dense frustrated magnets can be understood.

  6. Progressive freezing of interacting spins in isolated finite magnetic ensembles

    Science.gov (United States)

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

    2017-02-01

    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.

  7. Picosecond Spin Seebeck Effect

    Science.gov (United States)

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

    2017-02-01

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

  8. Picosecond spin Seebeck effect

    OpenAIRE

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

    2016-01-01

    We report time-resolved magneto-optic Kerr effect measurements of the longitudinal spin Seebeck effect driven by an interfacial temperature difference between itinerant electrons and magnons. The measured time-evolution of spin accumulation induced by laser-excitation indicates transfer of angular momentum across Au/Y$_3$Fe$_5$O$_{12}$ and Cu/Y$_3$Fe$_5$O$_{12}$ interfaces on a picosecond time-scale. The product of spin-mixing conductance and interfacial spin Seebeck coefficient determined is...

  9. Spin Waves in Terbium

    DEFF Research Database (Denmark)

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

    1975-01-01

    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...

  10. Sol-Gel Glasses

    Science.gov (United States)

    Mukherjee, S. P.

    1985-01-01

    Multicomponent homogeneous, ultrapure noncrystalline gels/gel derived glasses are promising batch materials for the containerless glass melting experiments in microgravity. Hence, ultrapure, homogeneous gel precursors could be used to: (1) investigate the effect of the container induced nucleation on the glass forming ability of marginally glass forming compositions; and (2) investigate the influence of gravity on the phase separation and coarsening behavior of gel derived glasses in the liquid-liquid immiscibility zone of the nonsilicate systems having a high density phase. The structure and crystallization behavior of gels in the SiO2-GeO2 as a function of gel chemistry and thermal treatment were investigated. As are the chemical principles involved in the distribution of a second network former in silica gel matrix being investigated. The procedures for synthesizing noncrystalline gels/gel-monoliths in the SiO2-GeO2, GeO2-PbO systems were developed. Preliminary investigations on the levitation and thermal treatment of germania silicate gel-monoliths in the Pressure Facility Acoustic Levitator were done.

  11. Measurement of spin Hall effect of reflected light.

    Science.gov (United States)

    Qin, Yi; Li, Yan; He, Huanyu; Gong, Qihuang

    2009-09-01

    We have measured the spin-dependent nanometer-sized displacements of the spin Hall effect of the reflected light from a planar air-glass interface. In the case of the vertical polarization, the displacement is found to increase with the incident angle and subsequently decrease after approximately 48 deg, while in the case of the horizontal polarization, it changes rapidly near the Brewster angle. For a fixed incident angle of 30 deg, the displacement decreases to zero as the polarization angle approaches approximately 39 deg from 0 deg (the horizontal polarization) and then increases in the opposite direction until 90 deg (the vertical polarization).

  12. Bio-Glasses An Introduction

    CERN Document Server

    Jones, Julian

    2012-01-01

    This new work is dedicated to glasses and their variants which can be used as biomaterials to repair diseased and damaged tissues. Bio-glasses are superior to other biomaterials in many applications, such as healing bone by signaling stem cells to become bone cells.   Key features:  First book on biomaterials to focus on bio-glassesEdited by a leading authority on bio-glasses trained by one of its inventors, Dr Larry HenchSupported by the International Commission on Glass (ICG)Authored by members of the ICG Biomedical Glass Committee, with the goal of creating a seamless textb

  13. Glass strengthening and patterning methods

    Science.gov (United States)

    Harper, David C; Wereszczak, Andrew A; Duty, Chad E

    2015-01-27

    High intensity plasma-arc heat sources, such as a plasma-arc lamp, are used to irradiate glass, glass ceramics and/or ceramic materials to strengthen the glass. The same high intensity plasma-arc heat source may also be used to form a permanent pattern on the glass surface--the pattern being raised above the glass surface and integral with the glass (formed of the same material) by use of, for example, a screen-printed ink composition having been irradiated by the heat source.

  14. Glass formation - A contemporary view

    Science.gov (United States)

    Uhlmann, D. R.

    1983-01-01

    The process of glass formation is discussed from several perspectives. Particular attention is directed to kinetic treatments of glass formation and to the question of how fast a given liquid must be cooled in order to form a glass. Specific consideration is paid to the calculation of critical cooling rates for glass formation, to the effects of nucleating heterogeneities and transients in nucleation on the critical cooling rates, to crystallization on reheating a glass, to the experimental determination of nucleation rates and barriers to crystal nucleation, and to the characteristics of materials which are most conducive to glass formation.

  15. Heavy Metal Fluoride Glasses.

    Science.gov (United States)

    1987-04-01

    i 2N E ihhhhh1112h MEmhhhhEEEohhhhE I.’....momo 111111111’-20 LA ’Ll2. AFWL-TR-86-37 AFWL-TR- 86-37 oT C ,l C ’-’ N HEAVY METAL FLUORIDE GLASSES 0nI...Secwrit CkasmfcationJ HEAVY METAL FLUORIDE GLASSES 12. PERSONAL AUTHOR(S) Reisfield, Renata; and Eyal, Mrek 13. TYPE OF REPORT 113b. TIME COVERED 114...glasses containing about 50 mole% of ZrF4 [which can be replaced by HfF 4 or TIF 4 (Refs. 1-3) or heavy metal fluorides based on PbF2 and on 3d-group

  16. Relaxation in the glass former acetylsalicylic acid studied by deuteron magnetic resonance and dielectric spectroscopy

    Science.gov (United States)

    Nath, R.; El Goresy, T.; Geil, B.; Zimmermann, H.; Böhmer, R.

    2006-08-01

    Supercooled liquid and glassy acetylsalicylic acid was studied using dielectric spectroscopy and deuteron relaxometry in a wide temperature range. The supercooled liquid is characterized by major deviations from thermally activated behavior. In the glass the secondary relaxation exhibits the typical features of a Johari-Goldstein process. Via measurements of spin-lattice relaxation times the selectively deuterated methyl group was used as a sensitive probe of its local environments. There is a large difference in the mean activation energy in the glass with respect to that in crystalline acetylsalicylic acid. This can be understood by taking into account the broad energy barrier distribution in the glass.

  17. Nucleon Spin: Summary

    OpenAIRE

    Close, Frank

    1995-01-01

    This talk summarises the discussions during the conference on the spin structure of the nucleon held at Erice; July 1995. The summary focuses on where we have come, where we are now, and the emerging questions that direct where we go next in the quest to understand the nucleon spin.

  18. Antiferromagnetic spin Seebeck effect.

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-03-03

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

  19. Antiferromagnetic Spin Seebeck Effect

    Science.gov (United States)

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

    2016-03-01

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

  20. Single spin magnetic resonance

    Science.gov (United States)

    Wrachtrup, Jörg; Finkler, Amit

    2016-08-01

    Different approaches have improved the sensitivity of either electron or nuclear magnetic resonance to the single spin level. For optical detection it has essentially become routine to observe a single electron spin or nuclear spin. Typically, the systems in use are carefully designed to allow for single spin detection and manipulation, and of those systems, diamond spin defects rank very high, being so robust that they can be addressed, read out and coherently controlled even under ambient conditions and in a versatile set of nanostructures. This renders them as a new type of sensor, which has been shown to detect single electron and nuclear spins among other quantities like force, pressure and temperature. Adapting pulse sequences from classic NMR and EPR, and combined with high resolution optical microscopy, proximity to the target sample and nanoscale size, the diamond sensors have the potential to constitute a new class of magnetic resonance detectors with single spin sensitivity. As diamond sensors can be operated under ambient conditions, they offer potential application across a multitude of disciplines. Here we review the different existing techniques for magnetic resonance, with a focus on diamond defect spin sensors, showing their potential as versatile sensors for ultra-sensitive magnetic resonance with nanoscale spatial resolution.

  1. Physics lab in spin

    CERN Multimedia

    Hawkes, N

    1999-01-01

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

  2. Operator Spin Foam Models

    CERN Document Server

    Bahr, Benjamin; Kamiński, Wojciech; Kisielowski, Marcin; Lewandowski, Jerzy

    2010-01-01

    The goal of this paper is to introduce a systematic approach to spin foams. We define operator spin foams, that is foams labelled by group representations and operators, as the main tool. An equivalence relation we impose in the set of the operator spin foams allows to split the faces and the edges of the foams. The consistency with that relation requires introduction of the (familiar for the BF theory) face amplitude. The operator spin foam models are defined quite generally. Imposing a maximal symmetry leads to a family we call natural operator spin foam models. This symmetry, combined with demanding consistency with splitting the edges, determines a complete characterization of a general natural model. It can be obtained by applying arbitrary (quantum) constraints on an arbitrary BF spin foam model. In particular, imposing suitable constraints on Spin(4) BF spin foam model is exactly the way we tend to view 4d quantum gravity, starting with the BC model and continuing with the EPRL or FK models. That makes...

  3. Antiferromagnetic spin Seebeck Effect

    OpenAIRE

    Wu, SM; W. Zhang; Kc, A; Borisov, P.; Pearson, JE; Jiang, JS; Lederman, D.; Hoffmann, A.; Bhattacharya, A

    2015-01-01

    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 t...

  4. Fractionalized spin-wave continuum in kagome spin liquids

    Science.gov (United States)

    Mei, Jia-Wei; Wen, Xiao-Gang

    Motivated by spin-wave continuum (SWC) observed in recent neutron scattering experiments in Herbertsmithite, we use Gutzwiller-projected wave functions to study dynamic spin structure factor S (q , ω) of spin liquid states on the kagome lattice. Spin-1 excited states in spin liquids are represented by Gutzwiller-projected two-spinon excited wave functions. We investigate three different spin liquid candidates, spinon Fermi-surface spin liquid (FSL), Dirac spin liquid (DSL) and random-flux spin liquid (RSL). FSL and RSL have low energy peaks in S (q , ω) at K points in the extended magnetic Brillouin zone, in contrast to experiments where low energy peaks are found at M points. There is no obviuos contradiction between DSL and neutron scattering measurements. Besides a fractionalized spin (i.e. spin-1/2), spinons in DSL carry a fractionalized crystal momentum which is potentially detectable in SWC in the neutron scattering measurements.

  5. Foam Glass for Construction Materials

    DEFF Research Database (Denmark)

    Petersen, Rasmus Rosenlund

    2016-01-01

    Foaming is commonly achieved by adding foaming agents such as metal oxides or metal carbonates to glass powder. At elevated temperature, the glass melt becomes viscous and the foaming agents decompose or react to form gas, causing a foamy glass melt. Subsequent cooling to room temperature, result...... in a solid foam glass. The foam glass industry employs a range of different melt precursors and foaming agents. Recycle glass is key melt precursors. Many parameters influence the foaming process and optimising the foaming conditions is very time consuming. The most challenging and attractive goal is to make...... low density foam glass for thermal insulation applications. In this thesis, it is argued that the use of metal carbonates as foaming agents is not suitable for low density foam glass. A reaction mechanism is proposed to justify this result. Furthermore, an in situ method is developed to optimise...

  6. Spin transport at interfaces with spin-orbit coupling: Formalism

    Science.gov (United States)

    Amin, V. P.; Stiles, M. D.

    2016-09-01

    We generalize magnetoelectronic circuit theory to account for spin transfer to and from the atomic lattice via interfacial spin-orbit coupling. This enables a proper treatment of spin transport at interfaces between a ferromagnet and a heavy-metal nonmagnet. This generalized approach describes spin transport in terms of drops in spin and charge accumulations across the interface (as in the standard approach), but additionally includes the responses from in-plane electric fields and offsets in spin accumulations. A key finding is that in-plane electric fields give rise to spin accumulations and spin currents that can be polarized in any direction, generalizing the Rashba-Edelstein and spin Hall effects. The spin accumulations exert torques on the magnetization at the interface when they are misaligned from the magnetization. The additional out-of-plane spin currents exert torques via the spin-transfer mechanism on the ferromagnetic layer. To account for these phenomena we also describe spin torques within the generalized circuit theory. The additional effects included in this generalized circuit theory suggest modifications in the interpretations of experiments involving spin-orbit torques, spin pumping, spin memory loss, the Rashba-Edelstein effect, and the spin Hall magnetoresistance.

  7. Spin Hall and spin Nernst effects in graphene with intrinsic and Rashba spin-orbit interactions

    Institute of Scientific and Technical Information of China (English)

    Zhu Guo-Bao

    2012-01-01

    The spin Hall and spin Nernst effects in graphene are studied based on Green's function formalism.We calculate intrinsic contributions to spin Hall and spin Nernst conductivities in the Kane-Mele model with various structures.When both intrinsic and Rashba spin-orbit interactions are present,their interplay leads to some characteristics of the dependence of spin Hall and spin Nernst conductivities on the Fermi level.When the Rashba spin-orbit interaction is smaller than intrinsic spin-orbit coupling,a weak kink in the conductance appears.The kink disappears and a divergence appears when the Rashba spin-orbit interaction enhances.When the Rashba spin-orbit interaction approaches and is stronger than intrinsic spin-orbit coupling,the divergence becomes more obvious.

  8. Shattering women's glass ceiling

    OpenAIRE

    Camilleri Podesta, Marie Therese; Duca, Edward

    2013-01-01

    The role of women in academia has always greatly interested me. Several years ago, when I was asked to become Gender Issues Committee chairperson at the University of Malta, I readily accepted. http://www.um.edu.mt/think/shattering-womens-glass-ceiling/

  9. Glass as matter

    DEFF Research Database (Denmark)

    Beim, Anne

    2000-01-01

    Refraiming the Moderns - Substitute Windows and Glass. In general terms, the seminar has contributed to the growing interest in the problems concerning the restoration of Modern Movement architecture. More particularly, it has of course drawn our attention to modern windows, which are increasingly...

  10. What Glass Ceiling?

    Science.gov (United States)

    Lynch, Michael; Post, Katherine

    1996-01-01

    A recent study drawing on data from the Census Bureau and the Bureau of Labor Statistics suggests that the wage gap between men and women has virtually disappeared, and that the so-called "glass ceiling" results more from age and qualifications than from explicit discrimination. (SLD)

  11. Supercooled Liquids and Glasses

    OpenAIRE

    1999-01-01

    In these lectures, which were presented at "Soft and Fragile Matter, Nonequilibrium Dynamics, Metastability and Flow" University of St. Andrews, 8 July - 22 July, 1999, I give an introduction to the physics of supercooled liquids and glasses and discuss some computer simulations done to investigate these systems.

  12. Microchips on glass

    NARCIS (Netherlands)

    Keulemans, M.

    2007-01-01

    Microchips on glass. What about a mobile phone that uses a single microchip to receive all the available frequency bands, plus extras such as television, gps, and Internet access? Or, in due time, see-though implants that will monitor your state of health, and equipment that will let you see through

  13. Stained Glass and Flu

    Centers for Disease Control (CDC) Podcasts

    2017-02-01

    Dr. Robert Webster, an Emeritus member of the Department of Infectious Diseases at St. Jude Children's Research Hospital, discusses his cover art story on stained glass and influenza.  Created: 2/1/2017 by National Center for Emerging and Zoonotic Infectious Diseases (NCEZID).   Date Released: 2/1/2017.

  14. Triad ''Metal - Enamel - Glass''

    Science.gov (United States)

    Mukhina, T.; Petrova, S.; Toporova, V.; Fedyaeva, T.

    2014-10-01

    This article shows how to change the color of metal and glass. Both these materials are self-sufficient, but sometimes used together. For example, enameling. In this case, the adhesion between metal substrate and stekloobraznae enamel layer, which was conducted on a stretching and a bend, was tested.

  15. Glass ceilings of professionalisation.

    Science.gov (United States)

    Stott, Dawn L

    2016-04-01

    The term glass ceiling is a political term often used to describe an unbreakable barrier that isnot visible with the human eye, but it keeps minorities from rising up i.e. it is a barrier to minoritygroups, in the past (and sometimes still) for women, that stops them from achieving theirtrue potential.

  16. Stained-Glass Pastels

    Science.gov (United States)

    Laird, Shirley

    2009-01-01

    The author has always liked the look of stained-glass windows. Usually the designs are simplified and the shapes are easier for younger students to draw. This technique seemed to be the perfect place for her fifth-graders to try their hand at color mixing. The smaller spaces and simple shapes were just what she needed for this group. Her students…

  17. Stained Glass and Flu

    Centers for Disease Control (CDC) Podcasts

    2016-02-01

    Dr. Robert Webster, an Emeritus member of the Department of Infectious Diseases at St. Jude Children's Research Hospital, discusses his cover art story on stained glass and influenza.  Created: 2/1/2016 by National Center for Emerging and Zoonotic Infectious Diseases (NCEZID).   Date Released: 2/1/2016.

  18. "Stained Glass" Landscape Windows

    Science.gov (United States)

    Vannata, Janine

    2008-01-01

    Both adults and children alike marvel at the grand vivid stained-glass windows created by American artist Louis Comfort Tiffany. Today he is commonly recognized as one of America's most influential designers and artists throughout the last nineteenth and early twentieth century. In the lesson described in this article, students created their own…

  19. Bimodal Latex Effect on Spin-Coated Thin Conductive Polymer-Single-Walled Carbon Nanotube Layers.

    Science.gov (United States)

    Moradi, Mohammad-Amin; Larrakoetxea Angoitia, Katalin; van Berkel, Stefan; Gnanasekaran, Karthikeyan; Friedrich, Heiner; Heuts, Johan P A; van der Schoot, Paul; van Herk, Alex M

    2015-11-10

    We synthesize two differently sized poly(methyl methacrylate-co-tert-butyl acrylate) latexes by emulsion polymerization and mix these with a sonicated single-walled carbon nanotube (SWCNT) dispersion, in order to prepare 3% SWCNT composite mixtures. We spin-coat these mixtures at various spin-speed rates and spin times over a glass substrate, producing a thin, transparent, solid, conductive layer. Keeping the amount of SWCNTs constant, we vary the weight fraction of our smaller 30-nm latex particles relative to the larger 70-nm-sized ones. We find a maximum in the electrical conductivity up to 370 S/m as a function of the weight fraction of smaller particles, depending on the overall solid content, the spin speed, and the spin time. This maximum occurs at 3-5% of the smaller latex particles. We also find a more than 2-fold increase in conductivity parallel to the radius of spin-coating than perpendicular to it. Atomic force microscopy points at the existence of lanes of latex particles in the spin-coated thin layer, while large-area transmission electron microscopy demonstrates that the SWCNTs are aligned over a grid fixed on the glass substrate during the spin-coating process. We extract the conductivity distribution on the surface of the thin film and translate this into the direction of the SWCNTs in it.

  20. To Spin or Not to Spin?

    Institute of Scientific and Technical Information of China (English)

    Tina Boikos

    2008-01-01

    @@ The alarm has just gone off. Do I really have to get up? I wonder. Originally, signing up for an early-morning spinning class seemed like a good idea; it jump-starts the day with some well-needed exercise.