Calorimetric investigation of an yttrium-dysprosium spin glass

International Nuclear Information System (INIS)

Wenger, L.E.

1978-01-01

In an effort to compare the spin glass characteristics of yttrium--rare earth alloys with those of the noble-metal spin glasses, the susceptibility and heat capacity of Y/sub 0.98/Dy/sub 0.02/ have been measured in the temperature range 2.5--40 K. The low-field ac susceptibility measurement shows the characteristic cusp-like peak at 7.64 K. The magnetic specific heat of the same sample shows a peak at 7.0 K and may be qualitatively described as a semi-cusp. The magnetic entropy change from absolute zero to 7 K is approximately 0.52 of cR ln(2J+1). These results are qualitatively different than previous calorimetric results on the archetypal spin glasses, AuFe and CuMn, where rounded maxima are observed at temperatures above the spin glass transition temperatures

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.

Evidence for power-law spin-correlation decay from muon spin relaxation in AgMn spin-glass

International Nuclear Information System (INIS)

MacLaughlin, D.E.; Gupta, L.C.; Cooke, D.W.; Heffner, R.H.; Leon, M.; Schillaci, M.E.

1983-01-01

Muon spin relaxation measurements have been carried out below the ''glass'' temperature T/sub g/ in AgMn spin-glasses. The muon spin-lattice relaxation rate varies with field H as H/sup -0.46plus-or-minus0.05/ for 0.30< or =T/T/sub g/< or =0.66. This suggests that impurity-spin correlations decay with time as t/sup -nu/, νapprox. =0.54 +- 0.05, in contrast to the more usual exponential decay. The present data therefore agree quantitatively with the prediction νapprox. =(1/2) of mean-field dynamic theories

Thermal conductivity of a superconducting spin-glass

International Nuclear Information System (INIS)

Crisan, M.

1988-01-01

The temperature dependence of the thermal conductivity for a superconducting spin-glass is calculated, taking a short-range spin-spin interaction in a super-conductor carrying a uniform flow. The presence of the short-range interaction between frozen spins gives rise to a strong depression in the thermal conductivity

Critical properties of a simple spin glass model

International Nuclear Information System (INIS)

Aharony, A.; Imry, Y.

1976-01-01

The Mattis spin glass model is described as following from a particular quenched random solid solution picture, and its zero-field properties are discussed. The random field model is reviewed. The application to the spin glass problem is made and the more general scaling theory presented, and the limitations of the model are discussed

Magnetic excitations in CuMn spin-glass alloys

International Nuclear Information System (INIS)

Tsunoda, Y.; Kunitomi, N.; Cable, J.W.

1985-01-01

Recent neutron scattering measurements have helped to clarify two important features of CuMn spin glasses. Murani and co-workers have studied the dynamical behavior of spin-glass systems and have observed characteristic ferromagnetic spin correlations with a broad distribution of relaxation times and a dynamical freezing process. By means of the polarization analysis technique, Cable and co-workers have observed the coexistence of two types of magnetic short-range order (MSRO): one is a modulated-spin structure, and the other is a ferromagnetic cluster associated with the atomic short-range order (ASRO). These ordered regions produce diffraction maxima which are found at the (1 1/2 +/- delta 0) and the (1 1/2 0) reciprocal lattice points, respectively. Both of these observations seem to be essential for understanding the CuMn spin-glass system. However, the physical relationship of these properties is not yet understood. The authors have studied the inelastic scattering of neutrons around the magnetic diffuse peak positions of a Cu/sub 78.7/Mn/sub 21.3/ single crystal. The spin-glass freezing temperature of a CuMn alloy with this Mn concentration is estimated to be T/sub f/ approx. 90 K. Most of the data were taken by scanning along the [0 1 0] direction from the (1 0 0) to the (1 1 0) reciprocal lattice points

Portfolios with nonlinear constraints and spin glasses

Science.gov (United States)

Gábor, Adrienn; Kondor, I.

1999-12-01

In a recent paper Galluccio, Bouchaud and Potters demonstrated that a certain portfolio problem with a nonlinear constraint maps exactly onto finding the ground states of a long-range spin glass, with the concomitant nonuniqueness and instability of the optimal portfolios. Here we put forward geometric arguments that lead to qualitatively similar conclusions, without recourse to the methods of spin glass theory, and give two more examples of portfolio problems with convex nonlinear constraints.

Effects of finite size on spin glass dynamics

Science.gov (United States)

Sato, Tetsuya; Komatsu, Katsuyoshi

2010-12-01

In spite of comprehensive studies to clarify a variety of interesting phenomena of spin glasses, their understanding has been insufficiently established. To overcome such a problem, fabrication of a mesoscopic spin glass system, whose dynamics can be observed over the entire range to the equilibrium, is useful. In this review the challenges of research that has been performed up to now in this direction and our recent related studies are introduced. We have established to study the spin glass behaviour in terms of droplet picture using nanofabricated mesoscopic samples to some extent, but some problems that should be clarified have been left. Finally, the direction of some new studies is proposed to solve the problems.

The ferromagnetic-spin glass transition in PdMn alloys: symmetry breaking of ferromagnetism and spin glass studied by a multicanonical method.

Science.gov (United States)

Kato, Tomohiko; Saita, Takahiro

2011-03-16

The magnetism of Pd(1-x)Mn(x) is investigated theoretically. A localized spin model for Mn spins that interact with short-range antiferromagnetic interactions and long-range ferromagnetic interactions via itinerant d electrons is set up, with no adjustable parameters. A multicanonical Monte Carlo simulation, combined with a procedure of symmetry breaking, is employed to discriminate between the ferromagnetic and spin glass orders. The transition temperature and the low-temperature phase are determined from the temperature variation of the specific heat and the probability distributions of the ferromagnetic order parameter and the spin glass order parameter at different concentrations. The calculation results reveal that only the ferromagnetic phase exists at x glass phase exists at x > 0.04, and that the two phases coexist at intermediate concentrations. This result agrees semi-quantitatively with experimental results.

Algebraic topology of spin glasses

International Nuclear Information System (INIS)

Koma, Tohru

2011-01-01

We study the topology of frustration in d-dimensional Ising spin glasses with d ≥ 2 with nearest-neighbor interactions. We prove the following. For any given spin configuration, the domain walls on the unfrustration network are all transverse to a frustrated loop on the unfrustration network, where a domain wall is defined to be a connected element of the collection of all the (d - 1)-cells which are dual to the bonds having an unfavorable energy, and the unfrustration network is the collection of all the unfrustrated plaquettes. These domain walls are topologically nontrivial because they are all related to the global frustration of a loop on the unfrustration network. Taking account of the thermal stability for the domain walls, we can explain the numerical results that three- or higher-dimensional systems exhibit a spin glass phase, whereas two-dimensional ones do not. Namely, in two dimensions, the thermal fluctuations of the topologically nontrivial domain walls destroy the order of the frozen spins on the unfrustration network, whereas they do not in three or higher dimensions. This may be interpreted as a global topological effect of the frustrations.

Dynamical Properties of a Diluted Dipolar-Interaction Heisenberg Spin Glass

International Nuclear Information System (INIS)

Zhang Kai-Cheng; Liu Yong; Chi Feng

2014-01-01

Up to now the chirality is seldom studied in the diluted spin glass although many investigations have been performed on the site-ordered Edwards—Anderson model. By simulation, we investigate the dynamical properties of both the spin-glass and the chiral-glass phases in a diluted dipolar system, which was manifested to have a spin-glass transition by recent numerical study. By scaling we find that both phases have the same aging behavior and closer aging parameter μ. Similarly, the domains grow in the same way and both phases have a closer barrier exponent Ψ. It means that both the spins and the chirality have the same dynamical properties and they may freeze at the same temperature. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Low-field susceptibilities of rare-earth spin glass alloys

International Nuclear Information System (INIS)

Sarkissian, B.V.B.

1978-01-01

The low-field AC susceptibilities of the dilute rare-earth spin glass alloys Sc-Gd, Sc-Tb, Pr-Tb and Pr-Gd are reported and compared with low-field DC susceptibilities of the same samples. The similarities between their behaviour and that of Au-Fe spin glass alloys is also considered. When single-ion anisotropy is important, this can cause a dramatic broadening of the sharp peak. Broadening in the AC peak has also observed as the frequency of the deriving field is increased. These data can be qualitatively discussed in terms of a recent magnetic-cluster model for spin glasses. (author)

On modeling of statistical properties of classical 3D spin glasses

International Nuclear Information System (INIS)

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

2011-01-01

We study statistical properties of 3D classical spin glass layer of certain width and infinite length. The 3D spin glass is represented as an ensemble of disordered 1D spatial spin chains (SSC) where interactions are random between spin chains (nonideal ensemble of 1D SSCs). It is proved that in the limit of Birkhoff's ergodic hypothesis performance, 3D spin glasses can be generated by Hamiltonian of disordered 1D SSC with random environment. Disordered 1D SSC is defined on a regular lattice where one randomly oriented spin is put on each node of lattice. Also, it is supposed that each spin randomly interacts with six nearest-neighboring spins (two spins on lattice and four in the environment). The recurrent transcendental equations are obtained on the nodes of spin-chain lattice. These equations, combined with the Silvester conditions, allow step-by-step construction of spin chain in the ground state of energy where all spins are in the minimal energy of a classical Hamiltonian. On the basis of these equations an original high-performance parallel algorithm is developed for 3D spin glasses simulation. Distributions of different parameters of unperturbed spin glass are calculated. In particular, it is analytically proved and numerical calculations show that the distribution of spin-spin interaction constant in Heisenberg nearest-neighboring Hamiltonian model, as opposed to widely used Gauss-Edwards-Anderson distribution, satisfies the Levy alpha-stable distribution law which does not have variance. A new formula is proposed for construction of partition function in the form of a one-dimensional integral on the energy distribution of 1D SSCs

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–...

The spin glasses: the paradigm of the complex systems

International Nuclear Information System (INIS)

Ruiz-Lorenzo, J.J.

1997-01-01

The solution of the spin glasses in the Mean Field approximation gives some interesting characteristics such as the existence of an infinite number of pure states organized in an ultrametric way (like in Taxonomy). These properties raise the spin glasses to a paradigm of the complex systems. (Author) 7 refs

Rational decisions, random matrices and spin glasses

Science.gov (United States)

Galluccio, Stefano; Bouchaud, Jean-Philippe; Potters, Marc

We consider the problem of rational decision making in the presence of nonlinear constraints. By using tools borrowed from spin glass and random matrix theory, we focus on the portfolio optimisation problem. We show that the number of optimal solutions is generally exponentially large, and each of them is fragile: rationality is in this case of limited use. In addition, this problem is related to spin glasses with Lévy-like (long-ranged) couplings, for which we show that the ground state is not exponentially degenerate.

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.

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...

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.

Production of entropy on simplified dynamics in spin glass systems

CERN Document Server

Saakyan, D B

2001-01-01

In models of spin glasses one eliminates condition of extreme based on one of the order parameters. On the basis of the available expression for static sum one derived the effective hamiltonian for parameter and the appropriate energy. Relaxation of the system is studied as energy exchange between the degree of freedom related to the order slow parameter and with the rest of the system. At that level one may indicate point of glass capture within phase space on the basis of the static solutions. One studies p-spin model without magnetic field in case of replica symmetry violation. One studies dynamics of p-spin glass in magnetic field in replica-symmetrical phase. One studied model of spins with quadratic interaction when dynamic constants had temperature differing from temperature of space

Mean-field theory of spin-glasses with finite coordination number

Science.gov (United States)

Kanter, I.; Sompolinsky, H.

1987-01-01

The mean-field theory of dilute spin-glasses is studied in the limit where the average coordination number is finite. The zero-temperature phase diagram is calculated and the relationship between the spin-glass phase and the percolation transition is discussed. The present formalism is applicable also to graph optimization problems.

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

Indian Academy of Sciences (India)

Home; Journals; Pramana – Journal of Physics; Volume 58; Issue 2 ... Spin glasses; quantum phase transition; ferromagnetism; electron gas. ... 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 ...

Magnetization relaxation in spin glasses above transition point

International Nuclear Information System (INIS)

Zajtsev, I.A.; Minakov, A.A.; Galonzka, R.R.

1988-01-01

Magnetization relaxation of Cd 0.6 Zn 0.4 Cr 2 Se 4 and Cd 0.6 Mn 0.4 Te monocrystalline samples with T g =21 K and T g =12 K respectively and magnetic colloid is investigated. It is shown that magnetization inexponential relaxation detected experimentally in spin and dipole glasses is essentially higher than T g temperature transition. It is found that at temperatures higher than T g the essential difference is observed in behaviour of spin glasses with different Z and disorder types

Analogy between spin glasses and Yang--Mills fluids

International Nuclear Information System (INIS)

Holm, D.D.; Kupershmidt, B.A.

1988-01-01

A dictionary of correspondence is established between the dynamical variables for spin-glass fluid and Yang-Mills plasma. The Lie-algebraic interpretation of these variables is presented for the two theories. The noncanonical Poisson bracket for the Hamiltonian dynamics of an ideal spin glass is shown to be identical to that for the dynamics of a Yang--Mills fluid plasma, although the Hamiltonians differ for the two theories. This Poisson bracket is associated to the dual space of an infinite-dimensional Lie algebra of semidirect-product type

Spin freezing in the re-entrant spin glass FeNiMn close to the frustration limit

Energy Technology Data Exchange (ETDEWEB)

Pappas, Catherine [Hahn-Meitner-Institut, Glienickerstr. 100, 14109 Berlin (Germany); Klenke, Jens [Hahn-Meitner-Institut, Glienickerstr. 100, 14109 Berlin (Germany); Hesse, Juergen [Institut fuer Metallphysik und Nukleare Festkoerperphysik, Technische Universitaet Braunschweig, 38106 Braunschweig (Germany); Wagner, Volker [Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig (Germany)]. E-mail: volker.wagner@ptb.de

2007-07-15

In the invar alloy (Fe{sub 0.65}Ni{sub 0.35}){sub 1-} {sub x} Mn {sub x} we measured the magnetic form factor s(Q) and the intermediate scattering function s(Q,t) for a sample close to the critical Mn concentration (x {sub c}=0.139), at which the sample turns to a re-entrant spin glass phase. The aim was to check whether the magnetic behaviour would approach the Q-independent relaxation behaviour of a classical spin glass when x=x {sub c}. The experiment showed a quite similar spin freezing as for a more ferromagnetic sample with x=0.113. The intermediate scattering function and the form factor were determined by paramagnetic NSE. The normalized scattering function S(Q,t)=s(Q,t)/s(Q)=exp[(-{gamma}t) {sup n}] was fitted by stretched exponential decay. As a function of temperature T<200 K the inverse time constant {gamma} showed the change of more than four orders of magnitude from frozen spin glass (T=60 K to T=100 K), where the ferromagnetic phase occurred. In general, the inverse time constant is higher than in the more ferromagnetic sample as the frustration of the spins became larger. In the ferromagnetic phase S(Q,t) depended on 0.3spin diffusive behaviour remained in the re-entrant spin glass down to at least 60 K.

Zero-field NMR study on a spin glass: iron-doped 2H-niobium diselenide

International Nuclear Information System (INIS)

Chen, M.C.

1982-01-01

Spin echoes are used to study the 93 Nb NQR in 2H-NbSe 2 Fe/sub x/. Measured are (intensity) x (temperature), and T/sub 1P/ (spin-lattice relaxation parameter) and T 2 (spin-spin relaxation time) as a function of temperature. Data reveal dramatic differences between non-spin glass samples (x = 0, 0.25%, 1% and 5%) and spin glass samples (x = 8%, 10% and 12%). All of the NQR results and the model calculation of the correlation times of Fe spins are best described by the phase transition picture of spin glasses

Observation of the anisotropic spin-glass transition and transverse spin ordering in pseudo-brookite through muon spin relaxation

NARCIS (Netherlands)

Boekema, C.; Brabers, V.A.M.; Lichti, R.L.; Denison, A.B.; Cooke, D.W.; Heffner, R.H.; Hutson, R.L.; Schillaci, M.E.; MacLaughlin, D.E.; Dodds, S.A.

1986-01-01

Zero-field longitudinal muon-spin-relaxation (µSR) experiments have been performed on single crystals of pseudo-brookite (Fe2-xTil+x O 5; x=0.25), an anisotropic spin-glass system. The spinglass temperature (Tg) is determined to be 44.0±0.5K. Above Tg, a distinct exponential muon-spin-relaxation

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.

Stimulated nuclear spin echos and spectral diffusion in glasses

International Nuclear Information System (INIS)

Borges, N.M.; Engelsberg, M.

1984-01-01

Experimental results of stimulated nuclear spin echos decay in glasses are presented. The measurements were performed in B 2 O 3 glasses, at the 23Na and 11 B resonance lines. The data analysis allows the study of Spectral diffusion at an inhomogeneous nuclear magnetic (NMR) resonance line, broadened for a desordered system of nuclear spins. A model is proposed to explain the time constants, and the particular form of the decay. (A.C.A.S.) [pt

The pseudo‐brookite spin‐glass system studied by means of muon spin relaxation

NARCIS (Netherlands)

Brabers, V.A.M.; Boekema, C.; Lichti, R.L.; Denison, A.B.; Cooke, D.W.; Heffner, R.H.; Hutson, R.L.; Schillaci, M.E.; MacLaughlin, D.E.

1987-01-01

Zero-field muon spin relaxation (µSR) experiments have been performed on the spin glass Fe1.75Ti1.25O5. Above the spin-glass temperature of 44 K a distinct exponential µSR rate (¿) is observed, while below Tg a square-root exponential decay occurs, indicating fast spin fluctuations. Near 8 K, a

Spin glasses and neural networks

International Nuclear Information System (INIS)

Parga, N.; Universidad Nacional de Cuyo, San Carlos de Bariloche

1989-01-01

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.)

Evolution of ferromagnetic interactions from cluster spin glass state in Co–Ga alloy

Energy Technology Data Exchange (ETDEWEB)

Mohammad Yasin, Sk. [Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India); Saha, Ritwik [Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai 400005 (India); Srinivas, V., E-mail: veeturi@iitm.ac.in [Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India); Kasiviswanathan, S. [Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India); Nigam, A.K. [Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai 400005 (India)

2016-11-15

Low temperature magnetic properties of binary Co{sub x}Ga{sub 100−x} (x=54–57) alloy have been investigated. Analysis of frequency dependence of ac susceptibility provided a conclusive evidence for the existence of cluster spin glass like behavior with the freezing temperature ~8, 14 K for x=54, 55.5 respectively. The parameters for conventional ‘slowing down’ of the spin dynamics have been extracted from the acs data, which confirm the presence of glassy phase. The magnitude of Mydosh parameter obtained from the fits is larger than that reported for typical canonical spin glasses and smaller than those for non-interacting ideal superparamagnetic systems but comparable to those of known cluster-glass systems. Memory phenomena using specific cooling protocols also support the spin-glass features in Co{sub 55.5}Ga{sub 44.5} composition. Further the development of ferromagnetic clusters from the cluster spin glass state has been observed in x=57 composition. - Highlights: • Temperature dependence of DC and AC susceptibility (acs) analysis has been carried out on Co{sub x}Ga{sub 1−x,} (x=54–57). • M–H data above transition suggests presence of spin clusters. • A detailed analysis of acs data suggests a cluster glass behavior as oppose to SPM state for x=54 and 55.5. • Memory phenomena using specific cooling protocols also support the spin-glass features in Co{sub 55.5}Ga{sub 44.5} composition. • Development of ferromagnetic like behavior for x≥57 has been suggested from DC and AC magnetization data.

Percolation and spin glass transition

International Nuclear Information System (INIS)

Sadiq, A.; Tahir-Kheli, R.A.; Wortis, M.; Bhatti, N.A.

1980-10-01

The behaviour of clusters of curved and normal plaquette particles in a bond random, +-J, Ising model is studied in finite square and triangular lattices. Computer results for the concentration of antiferromagnetic bonds when percolating clusters first appears are found to be close to those reported for the occurrence and disappearance of spin glass phases in these systems. (author)

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.

Experimental evidence for dynamic scaling in spin glasses

CERN Document Server

Pappas, C; Ehlers, G; Campbell, I A

2002-01-01

Dynamics is the key to the understanding of glassy transitions. A detailed analysis of s(Q,t) in the spin glass system Au sub 0 sub . sub 8 sub 6 Fe sub 0 sub . sub 1 sub 4 shows that at T sub g the autocorrelation function decays as t sup - sup x , with x propor to 0.12. Above T sub g , s(Q,t) is then described by the form proposed by Ogielski: t sup - sup x exp(-(t/tau sub 0) supbeta). These results agree with predictions of large scale numerical simulations and are a direct confirmation of dynamic scaling in spin glasses. (orig.)

Real-Space Application of the Mean-Field Description of Spin-Glass Dynamics

International Nuclear Information System (INIS)

Barrat, Alain; Berthier, Ludovic

2001-01-01

The out of equilibrium dynamics of finite dimensional spin glasses is considered from a point of view going beyond the standard 'mean-field theory' versus 'droplet picture' debate of the past decades. The main predictions of both theories concerning the spin-glass dynamics are discussed. It is shown, in particular, that predictions originating from mean-field ideas concerning the violations of the fluctuation-dissipation theorem apply quantitatively, provided one properly takes into account the role of a spin-glass coherence length, which plays a central role in the droplet picture. Dynamics in a uniform magnetic field is also briefly discussed

Spin-glass in low dimension and the Midgal Kadanoff approximation

International Nuclear Information System (INIS)

Curado, E.M.F.

1987-01-01

We study the spin glass problem within the Migdal Kadanoff approximation of the hyper cubic lattices. Using various technics, both analytical and numerical, we perform the real space renormalization of the problem. We find that a Spin Glass transition occurs in 3 dimensions while it does not occur in two dimensions. The specific heat critical exponent for the transition is found to be large and negative in agreement with the experimental results. (author) [pt

Low-field susceptibilities of rare earth spin glass alloys

International Nuclear Information System (INIS)

Sarkissian, B.V.B.

1977-01-01

Static susceptibility in various applied fields and AC susceptibility data on Sc 13% Gd and Sc 4.5% Tb spin glass alloys are reported. The data show that the sharp peak at the freezing temperature, Tsub(g), normally observed in the low-field susceptibility of spin glasses containing 3d magnetic impurities is observed here in the case of Gd, which is an S state solute, but not for Tb. On the contrary, for the Sc-Tb alloy a rather rounded maximum is observed which becomes slightly sharper with increasing applied magnetic fields. (author)

Simulations of ground state fluctuations in mean-field Ising spin glasses

International Nuclear Information System (INIS)

Boettcher, Stefan

2010-01-01

The scaling of fluctuations in the distribution of ground state energies or costs with the system size N for Ising spin glasses is considered using an extensive set of simulations with the extremal optimization heuristic across a range of different models on sparse and dense graphs. These models exhibit very diverse behaviors, and an asymptotic extrapolation is often complicated by higher-order corrections in size. The clearest picture, in fact, emerges from the study of graph bipartitioning, a combinatorial optimization problem closely related to spin glasses. Asides from two-spin interactions with discrete bonds, we also consider problems with Gaussian bonds and three-spin interactions, which behave quite differently

Size and field effect on mesoscopic spin glass

Energy Technology Data Exchange (ETDEWEB)

Komatsu, K. [Department of Applied Physics and Physico-Infomatics, Faculty of Science and Technology, Keio University, Yokohama 223-8522 (Japan)]. E-mail: komatsu@az.appi.keio.ac.jp; 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, 4259 Nagatsuta, Midori-ku, 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

Spin glass particles were prepared as the mesoscopic system in order to examine the space scale of spin glass domain (droplet). The peak temperature T {sub peak} in the temperature-dependent magnetization is systematically reduced with decreasing average particle size. This is due to the imitation of droplet growth to the particle diameter. The magnetic field H also decreases T {sub peak}, which is caused by the reduction of the barrier height by Zeeman energy. However, there appears different tendency in the relation between H and T {sub peak} below 100 Oe. This indicates the existence of crossover between the two regimes in which the free energy and Zeeman energy govern the droplet excitation.

Interaction-flip identities in spin glasses

NARCIS (Netherlands)

Contucci, P.; Giardinà, C.; Giberti, C.

2009-01-01

We study the properties of fluctuation for the free energies and internal energies of two spin glass systems that differ for having some set of interactions flipped. We show that their difference has a variance that grows like the volume of the flipped region. Using a new interpolation method, which

A novel approach to modelling non-exponential spin glass relaxation

Energy Technology Data Exchange (ETDEWEB)

Pickup, R.M. [School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT (United Kingdom)]. E-mail: r.cywinski@leeds.ac.uk; Cywinski, R. [School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT (United Kingdom); Pappas, C. [Hahn-Meitner Institut, Glienicker Strasse 100, 14109 Berlin (Germany)

2007-07-15

A probabilistic cluster model, originally proposed by Weron to explain the universal power law of dielectric relaxation, is shown to account for the non-exponential relaxation in spin glasses above T {sub g}. Neutron spin echo spectra measured for the cluster glass compound Co{sub 55}Ga{sub 45} are well described by the Weron relaxation function, {phi}(t)={phi} {sub o}(1+k(t/{tau}) {sup {beta}}){sup -1/k}, with the interaction parameter k scaling linearly with the non-Curie-Weiss susceptibility.

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

Energy Technology Data Exchange (ETDEWEB)

Ma, Ji; Chen, Kezheng, E-mail: kchen@qust.edu.cn

2016-05-15

In this study, room-temperature spin-glass behaviors were observed in flake-like oriented attached hematite (α-Fe{sub 2}O{sub 3}) and iron phosphate hydroxide hydrate (Fe{sub 5}(PO{sub 4}){sub 4}(OH){sub 3}·2H{sub 2}O) single crystals. Remarkably, their coercivity (H{sub C}) 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. - Highlights: • Room-temperature spin-glass state was found in 2D oriented attached single crystals. • Coercivity values were found to be almost invariable at different temperatures. • The spin topographic map was assumed as SPM “islands” isolated by SG-like “bridges”.

The Order Parameter in a Spin Glass

NARCIS (Netherlands)

Enter, A.C.D. van; Griffiths, Robert B.

1983-01-01

Various possible precise definitions of an Edwards-Anderson type of order parameter for an Ising model spin glass are considered, using boundary conditions for a finite system, states of an infinite system, and a duplicate-system approach. Several of these definitions are shown to yield identical

Exact properties of spin glasses. I. 2D supersymmetry and Nishimori's result

International Nuclear Information System (INIS)

Georges, A.; Le Doussal, P.; Hansel, D.

1985-01-01

We introduce an effective theory of interacting fermions and bosons in order to express the quenched internal energy of the 2D Ising spin glass. We show that an exact result derived by Nishimori appears, in this formulation, as a dimensional reduction due to the apparition of a supersymmetry. For a general Ising spin glass, this suggests new insights into the physical meaning of this exact result

Exploring the dynamics about the glass transition by muon spin relaxation and muon spin rotation

International Nuclear Information System (INIS)

Bermejo, F J; Bustinduy, I; Cox, S F J; Lord, J S; Cabrillo, C; Gonzalez, M A

2006-01-01

The capability of muon spin rotation and muon spin relaxation to explore dynamics in the vicinity of the glass transition is illustrated by results pertaining to three materials exhibiting two different glass-forming abilities. Measurements under transverse magnetic fields enable us to monitor the dynamics of muonium-labelled closed-shell molecules within the microsecond range. The results display the onset of stochastic molecular motions taking place upon crossing from below the glass-transition temperature. In turn, the molecular dynamics of radicals formed by addition of atomic muonium to unsaturated organic molecules can also be explored up to far shorter times by means of relaxation measurements under longitudinal fields. The technique is then shown to be capable of singling out stochastic reorientational motions from others, which usually are strongly coupled to them and usually dominate the material response when measured using higher-frequency probes such as neutron and light scattering

Interfaces and the Question of Regional Congruence in Spin Glasses

International Nuclear Information System (INIS)

Newman, C. M.; Stein, D. L.

2001-01-01

We present a general theorem restricting properties of interfaces between thermodynamic states and apply it to the spin glass excitations observed numerically by Krzakala and Martin and separately by Palassini and Young in spatial dimensions d=3,4. We show that such excitations, with interface dimension d s < d, cannot yield regionally congruent thermodynamic states. More generally, zero density interfaces of translation-covariant excitations cannot be pinned (by the disorder) in any d but rather must deflect to infinity in the thermodynamic limit. Additional consequences concerning regional congruence in spin glasses and other systems are discussed

Environment overwhelms both nature and nurture in a model spin glass

Science.gov (United States)

Middleton, A. Alan; Yang, Jie

We are interested in exploring what information determines the particular history of the glassy long term dynamics in a disordered material. We study the effect of initial configurations and the realization of stochastic dynamics on the long time evolution of configurations in a two-dimensional Ising spin glass model. The evolution of nearest neighbor correlations is computed using patchwork dynamics, a coarse-grained numerical heuristic for temporal evolution. The dependence of the nearest neighbor spin correlations at long time on both initial spin configurations and noise histories are studied through cross-correlations of long-time configurations and the spin correlations are found to be independent of both. We investigate how effectively rigid bond clusters coarsen. Scaling laws are used to study the convergence of configurations and the distribution of sizes of nearly rigid clusters. The implications of the computational results on simulations and phenomenological models of spin glasses are discussed. We acknowledge NSF support under DMR-1410937 (CMMT program).

Random complex automata: Analogy with spin glasses

International Nuclear Information System (INIS)

Flyvbjerg, H.

1986-12-01

Ab initio properties of random networks of automata have been studied statistically. A strikingly high degree of similarity is demonstrated between the multivalley structure of the basins of attraction of Kauffman's model and that of infinite range spin glasses. Results from simulations as well as exact analytical results are presented. (orig.)

Phase separation, clustering, and fractal characteristics in glass: A magic-angle-spinning NMR spin-lattice relaxation study

Science.gov (United States)

Sen, S.; Stebbins, J. F.

1994-07-01

A comparative study of the 29Si spin-lattice relaxation behavior (induced by trace amounts of paramagnetic dopants in the glass) in phase-separated Li2Si4O9 and monophasic Li2Si2O5 and Na2Si2O5 glasses has been made in order to understand the nature of clustering and the resulting intermediate-range ordering. Optically clear tetrasilicate and disilicate glasses were prepared with 500 to 2000 ppm of Gd2O3, a paramagnetic dopant. The constituent structural units (Q3 and Q4 species) in all tetrasilicate glasses show strong differential relaxation following a power-law behavior. This is due to preferential partitioning of Gd3+ into the lower silica (Q3-rich) regions of these glasses, indicating the presence of Q species clusters too small to produce optical opalescence (a few nm to perhaps tens of nm). Preliminary results on 6Li spin-lattice relaxation in these glasses support this hypothesis. Differential relaxation becomes more pronounced on annealing due to growth of such clusters. No such differential relaxation was observed in the monophase disilicate glasses. For spin-lattice relaxation induced by direct dipolar coupling to paramagnetic ions, the recovery of magnetization is proportional to time as M(t)~tα where α is a function of the dimensionality D of mass distribution of the constituent Q species around the Gd3+ paramagnetic centers in the glass. For tetrasilicate glasses D~=2.62+/-0.22 and the system behaves as a mass fractal up to a length scale of 2 to 3 nm. D is thus equal to, within error, the theoretical value of 2.6 for an infinite percolation cluster of one type of Q species in another. For disilicate glasses, D~=3.06+/-0.18 which indicates a three-dimensional (and thus nonfractal) mass distribution of the constituent Q species over the same length scale.

Spin-glass polyamorphism induced by a magnetic field in LaMnO3 single crystal

Science.gov (United States)

Eremenko, V. V.; Sirenko, V. A.; Baran, A.; Čižmár, E.; Feher, A.

2018-05-01

We present experimental evidence of field-driven transition in spin-glass state, similar to pressure-induced transition between amorphous phases in structural and metallic glasses, attributed to the polyamorphism phenomena. Cusp in temperature dependences of ac magnetic susceptibility of weakly disordered LaMnO3 single crystal is registered below the temperature of magnetic ordering. Frequency dependence of the cusp temperature proves its spin-glass origin. The transition induced by a magnetic field in spin-glass state, is manifested by peculiarity in dependence of cusp temperature on applied magnetic field. Field dependent maximum of heat capacity is observed in the same magnetic field and temperature range.

Observation of linear spin wave dispersion in the reentrant spin glass Fe sub 0 sub . sub 7 Al sub 0 sub . sub 3

CERN Document Server

Shapiro, S M; Raymond, S; Lee, S H; Motoya, K

2002-01-01

Fe sub 0 sub . sub 7 Al sub 0 sub . sub 3 is a reentrant spin glass, which undergoes a transition from a paramagnet to a disordered ferromagnet at T sub c propor to 500 K; at a lower temperature the spins progressively freeze and it exhibits a spin-glass-like behavior. In the ferromagnetic phase spin waves with a q sup 2 dispersion are observed at small q, which broaden rapidly and become diffusive beyond a critical wave vector q sub 0. On cooling the spin waves also disappear and a strong elastic central peak develops. For measurements around the (1,1,1) Bragg peak, a new sharp excitation is observed which has a linear dispersion behavior. It disappears above T sub c , but persists throughout the spin-glass phase. It is not present in the stoichiometric Fe sub 3 Al material. (orig.)

Nature of the spin-glass phase at experimental length scales

International Nuclear Information System (INIS)

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

2010-01-01

We present a massive equilibrium simulation of the three-dimensional Ising spin glass at low temperatures. The Janus special-purpose computer has allowed us to equilibrate, using parallel tempering, L = 32 lattices down to T ≈ 0.64T c . We demonstrate the relevance of equilibrium finite size simulations to understanding experimental non-equilibrium spin glasses in the thermodynamical limit by establishing a time-length dictionary. We conclude that non-equilibrium experiments performed on a timescale of 1 h can be matched with equilibrium results on L ≈ 110 lattices. A detailed investigation of the probability distribution functions of the spin and link overlap, as well as of their correlation functions, shows that Replica Symmetry Breaking is the appropriate theoretical framework for the physically relevant length scales. Besides, we improve over existing methodologies in ensuring equilibration in parallel tempering simulations

Spin Glass Models of Syntax and Language Evolution

OpenAIRE

Siva, Karthik; Tao, Jim; 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. W...

Manganite/Cuprate Superlattice as Artificial Reentrant Spin Glass

KAUST Repository

Ding, Junfeng; Cossu, Fabrizio; Lebedev, Oleg I.; Zhang, Yuqin; Zhang, Zhidong; Schwingenschlö gl, Udo; Wu, Tao

2016-01-01

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

Observation of spin-glass behavior in nickel adsorbed few layer graphene

International Nuclear Information System (INIS)

Mitra, Sreemanta; Mondal, Oindrila; Banerjee, Sourish; Chakravorty, Dipankar

2013-01-01

Nickel-adsorbed graphene was prepared by first synthesizing graphite oxide (GO) by modified Hummers' method and then reducing a solution containing both GO and Ni 2+ . Energy dispersive X-ray spectroscopy analysis showed 31 at. % nickel was present. Magnetization measurements under both dc and ac magnetic fields were carried out in the temperature range 2 K to 300 K. The zero field cooled and field cooled magnetization data showed a pronounced irreversibility at a temperature around 20 K. The analysis of the ac susceptibility data was carried out by both Vogel-Fulcher as well as power law. From dynamic scaling analysis, the microscopic flipping time τ 0 ∼10 −13 s and critical exponent zν=5.9±0.1 were found, indicating the presence of conventional spin glass in the system. The spin glass transition temperature was estimated as 19.5 K. Decay of thermoremanent magnetization was explained by stretched exponential function with a value of the exponent as 0.6. From the results, it is concluded that nickel adsorbed graphene behaves like a spin-glass.

Observation of spin-glass behavior in nickel adsorbed few layer graphene

Energy Technology Data Exchange (ETDEWEB)

Mitra, Sreemanta [MLS Professor of Physics' Unit, Indian Association for the Cultivation of Science, Kolkata-700032 (India); Department of Physics, University of Calcutta, Kolkata-700009 (India); Mondal, Oindrila [Department of Physics, M.U.C. Woman' s College, Burdwan (India); Banerjee, Sourish [Department of Physics, University of Calcutta, Kolkata-700009 (India); Chakravorty, Dipankar [MLS Professor of Physics' Unit, Indian Association for the Cultivation of Science, Kolkata-700032 (India)

2013-01-14

Nickel-adsorbed graphene was prepared by first synthesizing graphite oxide (GO) by modified Hummers' method and then reducing a solution containing both GO and Ni{sup 2+}. Energy dispersive X-ray spectroscopy analysis showed 31 at. % nickel was present. Magnetization measurements under both dc and ac magnetic fields were carried out in the temperature range 2 K to 300 K. The zero field cooled and field cooled magnetization data showed a pronounced irreversibility at a temperature around 20 K. The analysis of the ac susceptibility data was carried out by both Vogel-Fulcher as well as power law. From dynamic scaling analysis, the microscopic flipping time {tau}{sub 0}{approx}10{sup -13}s and critical exponent z{nu}=5.9{+-}0.1 were found, indicating the presence of conventional spin glass in the system. The spin glass transition temperature was estimated as 19.5 K. Decay of thermoremanent magnetization was explained by stretched exponential function with a value of the exponent as 0.6. From the results, it is concluded that nickel adsorbed graphene behaves like a spin-glass.

Comment on 'Spherical 2+p spin-glass model: An analytically solvable model with a glass-to-glass transition'

International Nuclear Information System (INIS)

Krakoviack, V.

2007-01-01

Guided by old results on simple mode-coupling models displaying glass-glass transitions, we demonstrate, through a crude analysis of the solution with one step of replica symmetry breaking (1RSB) derived by Crisanti and Leuzzi for the spherical s+p mean-field spin glass [Phys. Rev. B 73, 014412 (2006)], that the phase behavior of these systems is not yet fully understood when s and p are well separated. First, there seems to be a possibility of glass-glass transition scenarios in these systems. Second, we find clear indications that the 1RSB solution cannot be correct in the full glassy phase. Therefore, while the proposed analysis is clearly naive and probably inexact, it definitely calls for a reassessment of the physics of these systems, with the promise of potentially interesting developments in the theory of disordered and complex systems

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 0Stinchcombe 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.

± J D-vector spin glass phase diagram and critical behaviour

International Nuclear Information System (INIS)

Coutinho, S.; Lyra, M.L.

1988-01-01

The phase diagram and the correlation length exponents of the ± J D-Vector Spin-Glass model are studied in the framework of the real space mean field renormalization group method. The boundary between the spin-glass (SG) and the ferromagnetic (F) phases is obtained from the renormalization flow equations and shows a reentrant behaviour over the SG region. This re-entrance increases smoothly with the coordination number. Analytical expressions for the thermal and the correlation length exponents are calculated straight forwardly for all fixed points and figures are presented and compared with availables results from other methods and data. (author) [pt

Simplicity of state and overlap structure in finite-volume realistic spin glasses

International Nuclear Information System (INIS)

Newman, C.M.; Stein, D.L.

1998-01-01

We present a combination of heuristic and rigorous arguments indicating that both the pure state structure and the overlap structure of realistic spin glasses should be relatively simple: in a large finite volume with coupling-independent boundary conditions, such as periodic, at most a pair of flip-related (or the appropriate number of symmetry-related in the non-Ising case) states appear, and the Parisi overlap distribution correspondingly exhibits at most a pair of δ functions at ±q EA . This rules out the nonstandard mean-field picture introduced by us earlier, and when combined with our previous elimination of more standard versions of the mean-field picture, argues against the possibility of even limited versions of mean-field ordering in realistic spin glasses. If broken spin-flip symmetry should occur, this leaves open two main possibilities for ordering in the spin glass phase: the droplet-scaling two-state picture, and the chaotic pairs many-state picture introduced by us earlier. We present scaling arguments which provide a possible physical basis for the latter picture, and discuss possible reasons behind numerical observations of more complicated overlap structures in finite volumes. copyright 1998 The American Physical Society

Relationship between energy landscape and low-temperature dynamics of ±J spin glasses

International Nuclear Information System (INIS)

Kobe, S.; Krawczyk, J.

2004-01-01

Clusters and valleys in the exact low-energy landscape of finite Edwards-Anderson ±J spin glasses are related to the distribution of spin domains and free spins in the ground states. The time evolution of the spin correlation function reflects a walk through the landscape at a given temperature and shows typical glassy behaviour

Aging, rejuvenation and memory phenomena in spin glasses

Indian Academy of Sciences (India)

Spin glass; relaxation; aging; rejuvenation; memory. PACS Nos 75.10. .... the application of finite excitations, the long time needed to cool the sample down ..... wait at T − ∆T during t2 = 9000 s and finally re-heated to T for another short time t3 ...

Memory effect and super-spin-glass ordering in an aggregated nanoparticle sample

International Nuclear Information System (INIS)

Cador, O.; Grasset, F.; Haneda, H.; Etourneau, J.

2004-01-01

A system consisting of aggregated nonstoichiometric zinc ferrite nanoparticles has been studied using AC and DC magnetization measurements. A superparamagnetic-super-spin-glass phase transition at T g has been identified. The relaxation time diverges at T g and the nonlinear susceptibility shows an abrupt increase. The critical behavior vanishes when the nanoparticles are not in close contact. The observation of the memory effect identical to that which has been already discovered in canonical spin-glass supports the existence of a true thermodynamic transition in agglomerated magnetic nanoparticles

Coexistence of supersymmetric and supersymmetry-breaking states in spherical spin-glasses

International Nuclear Information System (INIS)

Annibale, Alessia; Gualdi, Giulia; Cavagna, Andrea

2004-01-01

The structure of states of the perturbed p-spin spherical spin-glass is analysed. At low enough free energy, metastable states have a supersymmetric structure, while at higher free energies the supersymmetry is broken. The transition between the supersymmetric and the supersymmetry-breaking phase is triggered by a change in the stability of states

Self-averaging correlation functions in the mean field theory of spin glasses

International Nuclear Information System (INIS)

Mezard, M.; Parisi, G.

1984-01-01

In the infinite range spin glass model, we consider the staggered spin σsub(lambda)associated with a given eigenvector of the interaction matrix. We show that the thermal average of sub(lambda)sup(2) is a self-averaging quantity and we compute it

A Kondo cluster-glass model for spin glass Cerium alloys

International Nuclear Information System (INIS)

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

2011-01-01

There are clear indications that the presence of disorder in Ce alloys, such as Ce(Ni,Cu) or Ce(Pd,Rh), is responsible for the existence of a cluster spin glass state which changes continuously into inhomogeneous ferromagnetism at low temperatures. We present a study of the competition between magnetism and Kondo effect in a cluster-glass model composed by a random inter-cluster interaction term and an intra-cluster one, which contains an intra-site Kondo interaction J k and an inter-site ferromagnetic one J 0 . The random interaction is given by the van Hemmen type of randomness which allows to solve the problem without the use of the replica method. The inter-cluster term is solved within the cluster mean-field theory and the remaining intra-cluster interactions can be treated by exact diagonalization. Results show the behavior of the cluster glass order parameter and the Kondo correlation function for several sizes of the clusters, J k , J 0 and values of the ferromagnetic inter-cluster average interaction I 0 . Particularly, for small J k , the magnetic solution is strongly dependent on I 0 and J 0 and a Kondo cluster-glass or a mixed phase can be obtained, while, for large J k , the Kondo effect is still dominant, both in good agreement with experiment in Ce(Ni,Cu) or Ce(Pd,Rh) alloys.

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.

Magnetoresistance in spin glass alloys: Theory and experiment

International Nuclear Information System (INIS)

Mookerjee, A.; Chowdhury, D.

1984-11-01

The magnetoresistance of spin glass alloys is examined within the percolation model of Mookerjee and Chowdhury (1983), the mode freezing model of Hertz (1983) and the constrained relaxation model of Palmer et al. (1984). All three models yield qualitatively similar results in excellent agreement with the experiments of Majumdar (1983, 1984) on AgMn. (author)

Spin glass transition in the rhombohedral LiNi1/3Mn1/3Co1/3O2

International Nuclear Information System (INIS)

Bie, Xiaofei; Yang, Xu; Han, Bing; Chen, Nan; Liu, Lina; Wei, Yingjin; Wang, Chunzhong; Chen, Hong; Du, Fei; Chen, Gang

2013-01-01

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 1/3 Mn 1/3 Co 1/3 O 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

Field-theoretical description of itinerant spin glasses

International Nuclear Information System (INIS)

Kolley, E.; Kolley, W.

1986-01-01

By means of functional integral technique at T 0 the disordered Hubbard model is bosonized, resulting in an effective action of the Ginzburg-Landau type. The quenched-averaged free energy of the itinerant spin glass is calculated by using the replica trick and Bogolyubov's variational principle. The spinglass order parameter and the local magnetic moment fulfil a system of self-consistent equations in the presence of spatial fluctuations. (author)

Analytical evidence for the absence of spin glass transition on self-dual lattices

International Nuclear Information System (INIS)

Ohzeki, Masayuki; Nishimori, Hidetoshi

2009-01-01

We show strong evidence for the absence of a finite-temperature spin glass transition for the random-bond Ising model on self-dual lattices. The analysis is performed by an application of duality relations, which enables us to derive a precise but approximate location of the multicritical point on the Nishimori line. This method can be systematically improved to presumably give the exact result asymptotically. The duality analysis, in conjunction with the relationship between the multicritical point and the spin glass transition point for the symmetric distribution function of randomness, leads to the conclusion of the absence of a finite-temperature spin glass transition for the case of symmetric distribution. The result is applicable to the random-bond Ising model with ±J or Gaussian distribution and the Potts gauge glass on the square, triangular and hexagonal lattices as well as the random three-body Ising model on the triangular and the Union-Jack lattices and the four-dimensional random plaquette gauge model. This conclusion is exact provided that the replica method is valid and the asymptotic limit of the duality analysis yields the exact location of the multicritical point. (fast track communication)

Absence of aging in the remanent magnetization in Migdal-Kadanoff spin glasses

International Nuclear Information System (INIS)

Ricci-Tersenghi, F.; Ritort, F.

2000-04-01

We study the non-equilibrium behavior of three-dimensional spin glasses in the Migdal-Kadanoff approximation. This approximation is exact for disordered hierarchical lattices which have a unique ground state and equilibrium properties correctly described by the droplet model. Extensive numerical simulations show that this model lacks aging in the remanent magnetization as well as a maximum in the magnetic viscosity in disagreement with experiments as well as with numerical studies of the Edwards-Anderson model. This result strongly limits the validity of the droplet model (at least in its simplest form) as a good model for real spin glasses. (author)

Zero and finite field μSR spin glass Ag:Mn

International Nuclear Information System (INIS)

Brown, J.A.; Heffner, R.H.; Leon, M.; Olsen, C.E.; Schillaci, M.E.; Dodds, S.A.; Estle, T.L.; MacLaughlin, D.E.

1981-01-01

In this paper we present μSR data taken in both zero and finite fields for a Ag:Mn (1.6 at%) spin glass sample. The data allow us to determine, in the context of a particular model, the fluctuation rate of the Mn ions as a function of temperature. This rate decreases smoothly but very rapidly near the glass temperature, Tsub(g). The corresponding behavior in Cu:Mn is more gradual. (orig.)

Theory of spin-lattice relaxation of diffusing light nuclei in glasses

International Nuclear Information System (INIS)

Schirmer, A.; Schirmacher, W.

1988-01-01

NMR data of diffusion-induced spin-lattice relaxation in glasses cannot generally be interpreted in the framework of the classical theory of Bloembergen, Purcell and Pound (BPP). Since it is based on exponential density relaxation, generally bnot found in glasses, the BPP formula must be generalized. Here a combination of standard relaxation theory with a hopping model for diffusion in glasses is present. It is shown that the observed anomaties in the NMR data can be explained as a result of anomalous diffusion. 25 refs.; 1 figure

Correlation between magnetoresistance and magnetization in Ag Mn and Au Mn spin glasses

International Nuclear Information System (INIS)

Majumdar, A.K.

1982-08-01

Magnetization has been measured between 2 and 77 K and mostly up to fields of 20 K Oe in Ag Mn (1.1 and 5.4 at %) and Au Mn (1.8 and 4.6 at %) spin glass samples where the transverse magnetoresistance was measured earlier. It is found for the first time over a wide range of temperature and magnetic field that the negative magnetoresistance varies as the square of the bulk magnetization resulting in an universal curve in the spin glass regime. A theoretical justification is provided in terms of exciting theories. (author)

Glass transition in the spin-density wave phase of (TMTSF)2PF6

DEFF Research Database (Denmark)

Lasjaunias, J.C.; Biljakovic, K.; Nad, F.

1994-01-01

We present the results of low frequency dielectric measurements and a detailed kinetic investigation of the specific heat anomaly in the spin-density wave phase of (TMTSF)(2)PF6 in the temperature range between 2 and 4 K. The dielectric relaxation shows a critical slowing down towards a ''static'......'' glass transition around 2 K. The jump in the specific heat in different controlled kinetic conditions shows all the characteristics of freezing in supercooled liquids. Both effects give direct evidence of a glass transition in the spin-density wave ground state....

Phenomenological approach to the spin glass state of (Cu-Mn, Ag-Mn, Au-Mn and Au-Fe) alloys at low temperatures

International Nuclear Information System (INIS)

Al-Jalali, Muhammad A.; Kayali, Fawaz A.

2000-01-01

Full text.The spin glass of: (Cu-Mn, Ag-Mn, Au-Mn, Au-Fe) alloys has been extensively studied. The availability of published and assured experimental data on the susceptibility x(T) of this alloys has enabled the design and application of phenomenological approach to the spin glass state of these interesting alloys. The use of and advanced (S.P.S.S) computer software has resulted revealing some important features of the spin glass in these alloys, the most important of which is that the spin glass state do not represent as phase change

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...

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.

Spin-glass state in the mixed system (Co1-xFex)2(OH)3Cl on deformed pyrochlore lattice

International Nuclear Information System (INIS)

Fujihala, M.; Hagihala, M.; Zheng, X.G.; Kawae, T.

2009-01-01

Magnetic interactions in a new geometrically frustrated system (Co 1-x Fe x ) 2 (OH) 3 Cl are investigated using magnetic susceptibility and μSR study. While Co 2 (OH) 3 Cl is ferromagnetic and Fe 2 (OH) 3 Cl antiferromagnetic, the partially substituted series (Co 1-x Fe x ) 2 (OH) 3 Cl show spin-glass behaviours, wherein ferromagnetic interactions prevail for low Fe concentration and antiferromagnetic ones prevail for high Fe concentration. In special, analysis of the AC magnetic susceptibility and ZF-μ + SR for the x=0.5 sample suggest that CoFe(OH) 3 Cl has both features of chemically disordered random spin glass and geometrically frustrated spin glass. It is also the first spin-glass system for the newly found geometric frustration series M 2 (OH) 3 X.

Spin glass transition in canonical AuFe alloys: A numerical study

International Nuclear Information System (INIS)

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

2012-01-01

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. -- Highlights: ► By simulation we investigated the abnormal critical exponents observed in canonical SG alloys. ► The critical exponents obtained from our simulations agree well with those measured from experiments. ► Our results strongly support that RKKY interactions lead to SG transitions at finite temperatures.

An electron spin resonance study of bis(tetraphenylarsonium) pentakis(isothiocyanato)nitrosyltechnetate(II): a six-co-ordinate low-spin 4d5 technetium(II) complex

International Nuclear Information System (INIS)

Baldas, J.; Boas, J.F.; Bonnyman, J.; Williams, G.A.

1984-01-01

The e.s.r. spectrum of the title complex has been studied in non-aqueous solution in the liquid and frozen glass phases. The spectrum is characteristic of a low-spin 4d 5 technetium(II) ion in an axially symmetric environment: g and A values are reported. The small quadrupole interaction observed is solvent dependent. A simple crystal field model, in which the unpaired electron is located in the tsub(2g) orbital triplet, is able to explain most features of the e.s.r. spectrum. A consideration of the electronic parameters derived from the g and A values leads to the conclusion that the results are best explained by a large tetragonal distortion from octahedral symmetry with strong π bonding between technetium and the ligands. (author)

Parisi function for two spin glass models

International Nuclear Information System (INIS)

Sibani, P.; Hertz, J.A.

1984-01-01

The probability distribution function P(q) for the overlap of pairs of metastable states and the associated Parisi order function q(x) are calculated exactly at zero temperature for two simple models. The first is a chain in which each spin interacts randomly with the sum of all the spins between it and one end of the chain; the second is an infinite-range limit of a spin glass version of Dyson's hierarchical model. Both have nontrivial overlap distributions: In the first case the problem reduces to a variable-step-length random walk problem, leading to q(x)=sin(πx). In the second model P(q) can be calculated by a simple recursion relation which generates devil's staircase structure in q(x). If the fraction p of antiferromagnetic bonds is less than 1/√2, the staircase is complete and the fractal dimensionality of the complement of the domain where q(x) is flat is log 2/log (1/p 2 ). In both models the space of metastable states can be described in terms of Cayley trees, which however have a different physical interpretation than in the S.K. model. (orig.)

Muon spin relaxation measurements of the fluctuation modes in spin-glass AgNm

Energy Technology Data Exchange (ETDEWEB)

Heffner, R.H.; Leon, M.; Schillaci, M.E.; MacLaughlin, D.E.; Dodds, S.A.

1983-01-01

Recently reported zero-field ..mu..SR measurements below the spin-glass transition temperature in AgMn (1.6 at%) show a temperature dependent inhomogeneous width. The authors discuss these data in terms of a model in which the local field undergoes limited-amplitude fluctuations. The authors find that both very slow (approx. = 0.3 ..mu..s/sup -1/) and rapid (approx. = 3000 ..mu..s/sup -1/) fluctuations are required. 10 references, 1 figure, 1 table.

Population annealing: Theory and application in spin glasses

OpenAIRE

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

2015-01-01

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 ...

Low-temperature spin dynamics of a valence bond glass in Ba2YMoO6

Science.gov (United States)

de Vries, M. A.; Piatek, J. O.; Misek, M.; Lord, J. S.; Rønnow, H. M.; Bos, J.-W. G.

2013-04-01

We carried out ac magnetic susceptibility measurements and muon spin relaxation spectroscopy on the cubic double perovskite Ba2YMoO6, down to 50 mK. Below ∼1 K the muon relaxation is typical of a magnetic insulator with a spin-liquid type ground state, i.e. without broken symmetries or frozen moments. However, the ac susceptibility revealed a dilute-spin-glass-like transition below ∼1 K. Antiferromagnetically coupled Mo5+ 4d1 electrons in triply degenerate t2g orbitals are in this material arranged in a geometrically frustrated fcc lattice. Bulk magnetic susceptibility data has previously been interpreted in terms of a freezing to a heterogeneous state with non-magnetic sites where 4d1 electrons have paired in spin-singlets dimers, and residual unpaired Mo5+ 4d1 electron spins. Based on the magnetic heat capacity data it has been suggested that this heterogeneity is the result of kinetic constraints intrinsic to the physics of the pure system (possibly due to topological overprotection) leading to a self-induced glass of valence bonds between neighbouring 4d1 electrons. The muon spin relaxation (μSR) unambiguously points to a heterogeneous state with a static arrangement of unpaired electrons in a background of (valence bond) dimers between the majority of Mo5+ 4d electrons. The ac susceptibility data indicate that the residual magnetic moments freeze into a dilute-spin-glass-like state. This is in apparent contradiction with the muon-spin decoupling at 50 mK in fields up to 200 mT, which indicates that, remarkably, the time scale of the field fluctuations from the residual moments is ∼5 ns. Comparable behaviour has been observed in other geometrically frustrated magnets with spin-liquid-like behaviour and the implications of our observations on Ba2YMoO6 are discussed in this context.

Inverse freezing in the Hopfield fermionic Ising spin glass with a transverse magnetic field

International Nuclear Information System (INIS)

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

2011-01-01

The Hopfield fermionic Ising spin glass (HFISG) model in the presence of a magnetic transverse field Γ is used to study the inverse freezing transition. The mean field solution of this model allows introducing a parameter a that controls the frustration level. Particularly, in the present fermionic formalism, the chemical potential μ and the Γ provide a magnetic dilution and quantum spin flip mechanism, respectively. Within the one step replica symmetry solution and the static approximation, the results show that the reentrant transition between the spin glass and the paramagnetic phases, which is related to the inverse freezing for a certain range of μ, is gradually suppressed when the level of frustration a is decreased. Nevertheless, the quantum fluctuations caused by Γ can destroy this inverse freezing for any value of a.

Possible description of domain walls in two-dimensional spin glasses by stochastic Loewner evolutions

International Nuclear Information System (INIS)

Bernard, Denis; Le Doussal, Pierre; Middleton, A. Alan

2007-01-01

Domain walls for spin glasses are believed to be scale invariant; a stronger symmetry, conformal invariance, has the potential to hold. The statistics of zero-temperature Ising spin glass domain walls in two dimensions are used to test the hypothesis that these domain walls are described by a Schramm-Loewner evolution SLE κ . Multiple tests are consistent with SLE κ , where κ=2.32±0.08. Both conformal invariance and the domain Markov property are tested. The latter does not hold in small systems, but detailed numerical evidence suggests that it holds in the continuum limit

Atomic Fermi-Bose mixtures in inhomogeneous and random lattices: From Fermi glass to quantum spin glass and quantum percolation

International Nuclear Information System (INIS)

Sanpera, A.; Lewenstein, M.; Kantian, A.; Sanchez-Palencia, L.; Zakrzewski, J.

2004-01-01

We investigate strongly interacting atomic Fermi-Bose mixtures in inhomogeneous and random optical lattices. We derive an effective Hamiltonian for the system and discuss its low temperature physics. We demonstrate the possibility of controlling the interactions at local level in inhomogeneous but regular lattices. Such a control leads to the achievement of Fermi glass, quantum Fermi spin-glass, and quantum percolation regimes involving bare and/or composite fermions in random lattices

On the use of spin glass concepts in random automata networks

Energy Technology Data Exchange (ETDEWEB)

Miranda, E N; Parga, N

1988-06-01

We apply concepts and techniques developed in the context of the mean-field theory of spin glasses to networks of random automata. This approach, proposed recently by Derrida and Flyvbjerg, may be useful in understanding the multivalley structure of the Kauffman model.

Spin-glass-like transition in the majority-vote model with anticonformists

Science.gov (United States)

Krawiecki, Andrzej

2018-03-01

Majority-vote model on scale-free networks and random graphs is investigated in which a randomly chosen fraction p of agents (called anticonformists) follows an antiferromagnetic update rule, i.e., they assume, with probability governed by a parameter q (0 transition from a disordered (paramagnetic) state to a spin-glass-like state, characterized by a non-zero value of the spin-glass order parameter measuring the overlap of agents' opinions in two replicas of the system, and simultaneously by the magnetization close to zero. In the case of the model on scale-free networks the critical value of the parameter q weakly depends on the details of the degree distribution. As p is decreased, the critical value of q falls quickly to zero and only the disordered phase is observed. On the other hand, for p close to zero for decreasing q the usual ferromagnetic transition is observed.

Efficient generation of series expansions for ±J Ising spin glasses in a classical or a quantum field

Science.gov (United States)

Singh, R. R. P.; Young, A. P.

2017-12-01

We discuss generation of series expansions for Ising spin glasses with a symmetric ±J (i.e., bimodal) distribution on d -dimensional hypercubic lattices using linked-cluster methods. Simplifications for the bimodal distribution allow us to go to higher order than for a general distribution. We discuss two types of problems, one classical and one quantum. The classical problem is that of the Ising spin glass in a longitudinal magnetic field h , for which we obtain high temperature series expansions in variables tanh(J /T ) and tanh(h /T ) . The quantum problem is a T =0 study of the Ising spin glass in a transverse magnetic field hT for which we obtain a perturbation theory in powers of J /hT . These methods require (i) enumeration and counting of all connected clusters that can be embedded in the lattice up to some order n , and (ii) an evaluation of the contribution of each cluster for the quantity being calculated, known as the weight. We discuss a general method that takes the much smaller list (and count) of all no free-end (NFE) clusters on a lattice up to some order n and automatically generates all other clusters and their counts up to the same order. The weights for finite clusters in both cases have a simple graphical interpretation that allows us to proceed efficiently for a general configuration of the ±J bonds and at the end perform suitable disorder averaging. The order of our computations is limited by the weight calculations for the high-temperature expansions of the classical model, while they are limited by graph counting for the T =0 quantum system. Details of the calculational methods are presented.

Stability and replica symmetry in the ising spin glass: a toy model

International Nuclear Information System (INIS)

De Dominicis, C.; Mottishaw, P.

1986-01-01

Searching for possible replica symmetric solutions in an Ising spin glass (in the tree approximation) we investigate a toy model whose bond distribution has two non vanishing cumulants (instead of one only as in a gaussian distribution)

Spin Crossover in Fe(II)-M(II) Cyanoheterobimetallic Frameworks (M = Ni, Pd, Pt) with 2-Substituted Pyrazines.

Science.gov (United States)

Kucheriv, Olesia I; Shylin, Sergii I; Ksenofontov, Vadim; Dechert, Sebastian; Haukka, Matti; Fritsky, Igor O; Gural'skiy, Il'ya A

2016-05-16

Discovery of spin-crossover (SCO) behavior in the family of Fe(II)-based Hofmann clathrates has led to a "new rush" in the field of bistable molecular materials. To date this class of SCO complexes is represented by several dozens of individual compounds, and areas of their potential application steadily increase. Starting from Fe(2+), square planar tetracyanometalates M(II)(CN)4(2-) (M(II) = Ni, Pd, Pt) and 2-substituted pyrazines Xpz (X = Cl, Me, I) as coligands we obtained a series of nine new Hofmann clathrate-like coordination frameworks. X-ray diffraction reveals that in these complexes Fe(II) ion has a pseudo-octahedral coordination environment supported by four μ4-tetracyanometallates forming its equatorial coordination environment. Depending on the nature of X and M, axial positions are occupied by two 2X-pyrazines (X = Cl and M(II) = Ni (1), Pd (2), Pt (3); X = Me and M(II) = Ni (4), Pd (5)) or one 2X-pyrazine and one water molecule (X = I and M(II) = Ni (7), Pd (8), Pt (9)), or, alternatively, two distinct Fe(II) positions with either two pyrazines or two water molecules (X = Me and M(II) = Pt (6)) are observed. Temperature behavior of magnetic susceptibility indicates that all compounds bearing FeN6 units (1-6) display cooperative spin transition, while Fe(II) ions in N5O or N4O2 surrounding are high spin (HS). Structural changes in the nearest Fe(II) environment upon low-spin (LS) to HS transition, which include ca. 10% Fe-N distance increase, lead to the cell expansion. Mössbauer spectroscopy is used to characterize the spin state of all HS, LS, and intermediate phases of 1-9 (see abstract figure). Effects of a pyrazine substituent and M(II) nature on the hyperfine parameters in both spin states are established.

Low-temperature spin dynamics of a valence bond glass in Ba2YMoO6

International Nuclear Information System (INIS)

De Vries, M A; Piatek, J O; Rønnow, H M; Misek, M; Lord, J S; Bos, J-W G

2013-01-01

We carried out ac magnetic susceptibility measurements and muon spin relaxation spectroscopy on the cubic double perovskite Ba 2 YMoO 6 , down to 50 mK. Below ∼1 K the muon relaxation is typical of a magnetic insulator with a spin-liquid type ground state, i.e. without broken symmetries or frozen moments. However, the ac susceptibility revealed a dilute-spin-glass-like transition below ∼1 K. Antiferromagnetically coupled Mo 5+ 4d 1 electrons in triply degenerate t 2g orbitals are in this material arranged in a geometrically frustrated fcc lattice. Bulk magnetic susceptibility data has previously been interpreted in terms of a freezing to a heterogeneous state with non-magnetic sites where 4d 1 electrons have paired in spin-singlets dimers, and residual unpaired Mo 5+ 4d 1 electron spins. Based on the magnetic heat capacity data it has been suggested that this heterogeneity is the result of kinetic constraints intrinsic to the physics of the pure system (possibly due to topological overprotection) leading to a self-induced glass of valence bonds between neighbouring 4d 1 electrons. The muon spin relaxation (μSR) unambiguously points to a heterogeneous state with a static arrangement of unpaired electrons in a background of (valence bond) dimers between the majority of Mo 5+ 4d electrons. The ac susceptibility data indicate that the residual magnetic moments freeze into a dilute-spin-glass-like state. This is in apparent contradiction with the muon-spin decoupling at 50 mK in fields up to 200 mT, which indicates that, remarkably, the time scale of the field fluctuations from the residual moments is ∼5 ns. Comparable behaviour has been observed in other geometrically frustrated magnets with spin-liquid-like behaviour and the implications of our observations on Ba 2 YMoO 6 are discussed in this context. (paper)

Magnetic cluster mean-field description of spin glasses in amorphous La-Gd-Au alloys

International Nuclear Information System (INIS)

Poon, S.J.; Durand, J.

1978-03-01

Bulk magnetic properties of splat-cooled amorphous alloys of composition La/sub 80-x/Gd/sub x/Au 20 (0 less than or equal to x less than or equal to 80) were studied. Zero-field susceptibility, high-field magnetization (up to 75 kOe) and saturated remanence were measured between 1.8 and 290 0 K. Data were analyzed using a cluster mean-field approximation for the spin-glass and mictomagnetic alloys (x less than or equal to 56). Mean-field theories can account for the experimental freezing-temperatures of dilute spin-glasses in which the Ruderman-Kittel-Kasuya-Yosida interaction is dominant. For the dilute alloys, the role of amorphousness on the magnetic interactions is discussed. By extending the mean-field approximation, the concentrated spin-glasses are represented by rigid ferromagnetic clusters as individual spin-entities interacting via random forces. Scaling laws for the magnetization M and saturation remanent magnetization M/sub rs/ are obtained and presented graphically for the x less than or equal to 32 alloys in which M/x = g(H/x*, T/x), M/sub rs/(T)/x = M/sub rs/(0)/x/ exp (-α*T/x/sup p/) where x* is the concentration of clusters, α* is a constant, and p is the freezing-temperature exponent given by T/sub M/ infinity x/sup p/. It is found that p = 1 and 1.3 for the regions 4 less than or equal to x less than or equal to 40 respectively. An attempt is also made to account for the freezing temperatures of concentrated spin glasses. The strength of the interaction among clusters is determined from high-field magnetization measurements using the Larkin-Smith method modified for clusters. It is shown that for the x < 24 alloys, the size of the clusters can be correlated to the structural short-range order in the amorphous state. More concentrated alloys are marked by the emergence of cluster percolation

Colorimeter determination of Fe(II)/Fe(III) ratio in glass

International Nuclear Information System (INIS)

Baumann, E.W.; Coleman, C.J.; Karraker, D.G.; Scott, W.H.

1987-01-01

A colorimetric method has been developed to determine the Fe(II)/Fe(III) ratio in glass containing nuclear waste. Fe(II) is stabilized with pentavalent vanadium during dissolution in sulfuric and hydrofluoric acids. The chromogen is FerroZine (Hach Chemical Company), which forms a magenta complex with Fe(II). The two-step color development consists of determining the Fe(II) by adding FerroZine, followed by determining total Fe after the Fe(III) present is reduced with ascorbic acid. The method was validated by analyzing mixtures of ferrous/ferric solutions and nonferrous glass frit, and by comparison with Moessbauer spectroscopy. The effect of gamma radiation was established. The procedure is generally applicable to nonradioactive materials such as minerals and other glasses

Dealing with correlated choices: how a spin-glass model can help political parties select their policies.

Science.gov (United States)

Moore, M A; Katzgraber, Helmut G

2014-10-01

Starting from preferences on N proposed policies obtained via questionnaires from a sample of the electorate, an Ising spin-glass model in a field can be constructed from which a political party could find the subset of the proposed policies which would maximize its appeal, form a coherent choice in the eyes of the electorate, and have maximum overlap with the party's existing policies. We illustrate the application of the procedure by simulations of a spin glass in a random field on scale-free networks.

Hyperscaling breakdown and Ising spin glasses: The Binder cumulant

Science.gov (United States)

Lundow, P. H.; Campbell, I. A.

2018-02-01

Among the Renormalization Group Theory scaling rules relating critical exponents, there are hyperscaling rules involving the dimension of the system. It is well known that in Ising models hyperscaling breaks down above the upper critical dimension. It was shown by Schwartz (1991) that the standard Josephson hyperscaling rule can also break down in Ising systems with quenched random interactions. A related Renormalization Group Theory hyperscaling rule links the critical exponents for the normalized Binder cumulant and the correlation length in the thermodynamic limit. An appropriate scaling approach for analyzing measurements from criticality to infinite temperature is first outlined. Numerical data on the scaling of the normalized correlation length and the normalized Binder cumulant are shown for the canonical Ising ferromagnet model in dimension three where hyperscaling holds, for the Ising ferromagnet in dimension five (so above the upper critical dimension) where hyperscaling breaks down, and then for Ising spin glass models in dimension three where the quenched interactions are random. For the Ising spin glasses there is a breakdown of the normalized Binder cumulant hyperscaling relation in the thermodynamic limit regime, with a return to size independent Binder cumulant values in the finite-size scaling regime around the critical region.

Spectral Gap Estimates in Mean Field Spin Glasses

Science.gov (United States)

Ben Arous, Gérard; Jagannath, Aukosh

2018-05-01

We show that mixing for local, reversible dynamics of mean field spin glasses is exponentially slow in the low temperature regime. We introduce a notion of free energy barriers for the overlap, and prove that their existence imply that the spectral gap is exponentially small, and thus that mixing is exponentially slow. We then exhibit sufficient conditions on the equilibrium Gibbs measure which guarantee the existence of these barriers, using the notion of replicon eigenvalue and 2D Guerra Talagrand bounds. We show how these sufficient conditions cover large classes of Ising spin models for reversible nearest-neighbor dynamics and spherical models for Langevin dynamics. Finally, in the case of Ising spins, Panchenko's recent rigorous calculation (Panchenko in Ann Probab 46(2):865-896, 2018) of the free energy for a system of "two real replica" enables us to prove a quenched LDP for the overlap distribution, which gives us a wider criterion for slow mixing directly related to the Franz-Parisi-Virasoro approach (Franz et al. in J Phys I 2(10):1869-1880, 1992; Kurchan et al. J Phys I 3(8):1819-1838, 1993). This condition holds in a wider range of temperatures.

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.

Study of ±J Ising spin glasses via multicanonical ensemble

International Nuclear Information System (INIS)

Celik, T.; Berg, B.

1993-03-01

The authors performed numerical simulations of 2D and 3D Edwards-Anderson spin glass models by using the recently developed multicanonical ensemble. The ergodicity times increase with the lattice size approximately as V 3 . The energy, entropy and other physical quantities are easily calculable at all temperatures from a single simulation. Their finite size scalings and the zero temperature limits are also explored

Low energy excitations in fermionic spin glasses: A quantum-dynamical image of Parisi symmetry breaking

International Nuclear Information System (INIS)

Oppermann, R.; Rosenow, B.

1997-10-01

We report large effects of Parisi replica permutation symmetry breaking (RPSB) on elementary excitations of fermionic systems with frustrated magnetic interactions. The electronic density of states is obtained exactly in the zero temperature limit for (K = 1)- step RPSB together with relations for arbitrary breaking K, which lead to a new fermionic and dynamical Parisi solution at K = ∞. The Ward identity for charge conservation indicates RPSB-effects on the conductivity in metallic quantum spin glasses. This implies that RPSB is essential for any fermionic system showing spin glass sections within its phase diagram. An astonishing similarity with a neural network problem is also observed. (author)

A method that reveals the multi-level ultrametric tree hidden in p -spin-glass-like systems

International Nuclear Information System (INIS)

Baviera, R; Virasoro, M A

2015-01-01

In the study of disordered models like spin glasses the key object of interest is the rugged energy hypersurface defined in configuration space. The statistical mechanics calculation of the Gibbs–Boltzmann partition function gives the information necessary to understand the equilibrium behavior of the system as a function of the temperature but is not enough if we are interested in the more general aspects of the hypersurface: it does not give us, for instance, the different degrees of ruggedness at different scales. In the context of the replica symmetry breaking (RSB) approach we discuss here a rather simple extension that can provide a much more detailed picture. The attractiveness of the method relies on the fact that it is conceptually transparent and the additional calculations are rather straightforward. We think that this approach reveals an ultrametric organisation with many levels in models like p-spin glasses when we include saddle points. In this first paper we present detailed calculations for the spherical p-spin glass model where we discover that the corresponding decreasing Parisi function q(x) codes this hidden ultrametric organisation. (paper)

Probing quantum spin glass like system with a double quantum dot

Science.gov (United States)

Koh, C. Y.; Kwek, L. C.

2016-06-01

We study the ground state properties of a 4-qubit spin glass like (SGL) chain with probes at the end of the chain and compare our results with the non-spin glass like (NSGL) case. The SGL is modeled as a spin chain with nearest-neighbor couplings, taking on normal variates with mean J and variance Δ2. The entanglement between the probes is used to detect any discontinuity in the ground state energy spectrum. For the NSGL case, it was found that the concurrence of the probes exhibits sharp transitions whenever there are abrupt changes in the energy spectrum. In particular, for the 4-qubit case, there is a sudden change in the ground state energy at an external magnetic field B of around 0.66 (resulting in a drop in concurrence of the probes) and 1.7 (manifest as a spike). The latter spike persists for finite temperature case. For the SGL sample with sufficiently large Δ, however, the spike is absent. Thus, an absence in the spike could act as a possible signature of the presence of SGL effects. Moreover, the sudden drop in concurrence at B ≈ 0.66 does not disappear but gets smeared with increasing Δ. However, this drop can be accentuated with a smaller probe coupling. The finite temperature case is also briefly discussed.

Experimental study of mixed ferromagnetic spin glass systems

International Nuclear Information System (INIS)

Mirebeau, I.

1987-01-01

The mixed ferromagnetic spin glass systems are characterized by a distribution of positive and negative exchange interactions whose maximum occurs at a positive value. We have undertaken an experimental study of amorphous (Fe 1-x Mn x ) .75 PBA1, polycrystalline and monocrystalline Ni 1-x Mn x and Au 1-x Fe x alloys. By Moessbauer effect, magnetization and neutron scattering, we show that below a ''canting'' temperature T K , spin components transverse to the mean magnetization become frozen. Small angle neutron scattering studies with an applied field show a magnetic ''structure'' i.e. the intensity exhibits a maximum at a finite q value for temperatures below T K . This structure has been studied as a function of temperature, applied field and concentration using both small angle neutron scattering and 3 axis spectrometry where we separate the elastic from the inelastic components. Possible interpretations of this new structure will be given [fr

Superconducting to spin-glass state transformation in β-pyrochlore KxOs2O6

Science.gov (United States)

Lee, C. C.; Lee, W. L.; Lin, J.-Y.; Tsuei, C. C.; Lin, J. G.; Chou, F. C.

2011-03-01

β-pyrochore KOs2O6, which shows superconductivity below ~9.7 K, has been converted into KxOs2O6 (x≲(2)/(3)-(1)/(2)) electrochemically to show spin-glass-like behavior below ~6.1 K. A room-temperature sample surface potential versus charge transfer scan indicates that there are at least two two-phase regions for x between 1 and 0.5. A rattling model of superconductivity for the title compound has been examined using electrochemical potassium de-intercalation. The significant reduction of superconducting volume fraction due to minor potassium reduction suggests the importance of defect and phase coherence in the rattling model. Magnetic susceptibility, resistivity, and specific heat measurement results have been compared between the superconducting and spin-glass-like samples.

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

International Nuclear Information System (INIS)

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

2016-01-01

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. (paper)

Legendre Duality of Spherical and Gaussian Spin Glasses

Energy Technology Data Exchange (ETDEWEB)

Genovese, Giuseppe, E-mail: giuseppe.genovese@math.uzh.ch [Universität Zürich, Institut für Mathematik (Switzerland); Tantari, Daniele, E-mail: daniele.tantari@sns.it [Scuola Normale Superiore di Pisa, Centro Ennio de Giorgi (Italy)

2015-12-15

The classical result of concentration of the Gaussian measure on the sphere in the limit of large dimension induces a natural duality between Gaussian and spherical models of spin glass. We analyse the Legendre variational structure linking the free energies of these two systems, in the spirit of the equivalence of ensembles of statistical mechanics. Our analysis, combined with the previous work (Barra et al., J. Phys. A: Math. Theor. 47, 155002, 2014), shows that such models are replica symmetric. Lastly, we briefly discuss an application of our result to the study of the Gaussian Hopfield model.

Legendre Duality of Spherical and Gaussian Spin Glasses

International Nuclear Information System (INIS)

Genovese, Giuseppe; Tantari, Daniele

2015-01-01

The classical result of concentration of the Gaussian measure on the sphere in the limit of large dimension induces a natural duality between Gaussian and spherical models of spin glass. We analyse the Legendre variational structure linking the free energies of these two systems, in the spirit of the equivalence of ensembles of statistical mechanics. Our analysis, combined with the previous work (Barra et al., J. Phys. A: Math. Theor. 47, 155002, 2014), shows that such models are replica symmetric. Lastly, we briefly discuss an application of our result to the study of the Gaussian Hopfield model

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.

High temperature spin-glass-like transition in La0.67Sr0.33MnO3 nanofibers near the Curie point.

Science.gov (United States)

Lu, Ruie; Yang, Sen; Li, Yitong; Chen, Kaiyun; Jiang, Yun; Fu, Bi; Zhang, Yin; Zhou, Chao; Xu, Minwei; Zhou, Xuan

2017-06-28

The glassy transition of superparamagnetic (SPM) (r glass-like (SGL) behavior near the Curie point (T C ), i.e., T 0 = 330 K, in La 0.67 Sr 0.33 MnO 3 (LSMO) nanofibers (NFs) composed of nanoparticles beyond the SPM size (r ≫ r 0 ), resulting in a significant increase of the glass transition temperature. This SGL transition near the T C of bulk LSMO can be explained to be the scenario of locally ordered clusters embedded in a disordered host, in which the assembly of nanoparticles has a magnetic core-shell model driven by surface spin glass. The presence of a surface spin glass of nanoparticles was proved by the Almeida-Thouless line δT f ∝ H 2/3 , exchange bias, and reduced saturation magnetization of the NF system. Composite dynamics were found - that is, both the SPM and the super-spin-glass (SSG) behavior are found in such an NF system. The bifurcation of the zero-field-cooled (ZFC) and field-cooled (FC) magnetization vs. temperature curves at the ZFC peak, and the flatness of FC magnetization involve SSG, while the frequency-dependent ac susceptibility anomaly follows the Vogel-Fulcher law that implies weak dipole interactions of the SPM model. This finding can help us to find a way to search for high temperature spin glass materials.

From near to eternity: Spin-glass planting, tiling puzzles, and constraint-satisfaction problems

Science.gov (United States)

Hamze, Firas; Jacob, Darryl C.; Ochoa, Andrew J.; Perera, Dilina; Wang, Wenlong; Katzgraber, Helmut G.

2018-04-01

We present a methodology for generating Ising Hamiltonians of tunable complexity and with a priori known ground states based on a decomposition of the model graph into edge-disjoint subgraphs. The idea is illustrated with a spin-glass model defined on a cubic lattice, where subproblems, whose couplers are restricted to the two values {-1 ,+1 } , are specified on unit cubes and are parametrized by their local degeneracy. The construction is shown to be equivalent to a type of three-dimensional constraint-satisfaction problem known as the tiling puzzle. By varying the proportions of subproblem types, the Hamiltonian can span a dramatic range of typical computational complexity, from fairly easy to many orders of magnitude more difficult than prototypical bimodal and Gaussian spin glasses in three space dimensions. We corroborate this behavior via experiments with different algorithms and discuss generalizations and extensions to different types of graphs.

Spin glass transition in a thin-film NiO/permalloy bilayer

Science.gov (United States)

Ma, Tianyu; Urazhdin, Sergei

2018-02-01

We experimentally study magnetization aging in a thin-film NiO/permalloy bilayer. Aging characteristics are nearly independent of temperature below the exchange bias blocking temperature TB, but rapidly vary above it. The dependence on the magnetic history qualitatively changes across TB. The observed behaviors are consistent with the spin glass transition at TB, with significant implications for magnetism and magnetoelectronic phenomena in antiferromagnet/ferromagnet bilayers.

Spin-glass behavior in the S=1/2 fcc ordered perovskite Sr2CaReO6

International Nuclear Information System (INIS)

Wiebe, C.R.; Greedan, J.E.; Luke, G.M.; Gardner, J.S.

2002-01-01

The ordered perovskite Sr 2 CaReO 6 of monoclinic symmetry [space group P2 1 /n,a=5.7556(3) A,b=5.8534(3) A,c=8.1317(4) A,β=90.276(5) deg. at T=4 K] has been synthesized using standard solid-state chemistry techniques. The difference in the size and charge of the cations induces an ordering of the B site Ca 2+ and Re 6+ ions which leads to a distorted fcc lattice of spin-(1/2) Re 6+ (5d 1 ) moments. dc magnetic susceptibility measurements indicate a maximum at T G ∼14 K and an irreversibility in the field-cooled and zero-field-cooled data at ∼22 K that is believed to be caused by the geometric frustration inherent in the fcc structure. Neutron-scattering measurements confirm the absence of magnetic long-range order, and muon spin relaxation experiments indicate the presence of an abrupt spin freezing at T G . Specific heat measurements reveal a broad anomaly typical of spin glasses and no sharp feature. 65% of the spin entropy is released at low temperatures. The low-temperature data do not show the expected linear temperature dependence, but rather a T 3 relationship, as is observed, typically, for antiferromagnetic spin waves. The material is characterized as an unconventional, essentially disorder-free, spin glass

Experimental evidence of spin glass and exchange bias behavior in sputtered grown α-MnO{sub 2} nanorods

Energy Technology Data Exchange (ETDEWEB)

Kumar, Ashwani; Sanger, Amit; Singh, Amit Kumar; Kumar, Arvind [Nanoscience Laboratory, Institute Instrumentation Centre, Indian Institute of Technology Roorkee, Roorkee 247667 (India); Kumar, Mohit [Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100 (Israel); Chandra, Ramesh [Nanoscience Laboratory, Institute Instrumentation Centre, Indian Institute of Technology Roorkee, Roorkee 247667 (India)

2017-07-01

Highlights: • We have synthesized the α-MnO{sub 2} nanorods by using DC reactive sputtering. • We observed Spin glass and exchange bias behavior at low temperature in sputtered grown α-MnO{sub 2} nanorods. • Exchange bias arises due to exchange coupling of uncompensated FM spins and AFM spins at FM/AFM interface. - Abstract: Here, we present a single-step process to synthesize the α-MnO{sub 2} nanorods forest using reactive DC magnetron sputtering for the application of magnetic memories. The structural and morphological properties of the α-MnO{sub 2} nanorods were systematically studied using numerous analytical techniques, including X-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy and transmission electron microscopy. The magnetic measurements suggest that the α-MnO{sub 2} nanorods exhibit spin glass and exchange bias behaviour at low temperature. Such low temperature behaviour is explained by the core-shell type structure of nanorods. Antiferromagnetic core and shell of uncompensated ferromagnetic spins leads to the formation of antiferromagnetic/ferromagnetic (AFM/FM) interfaces, which originates exchange bias in the sample.

Evidence for reentrant spin glass behavior in transition metal substituted Co-Ga alloys near critical concentration

Science.gov (United States)

Yasin, Sk. Mohammad; Srinivas, V.; Kasiviswanathan, S.; Vagadia, Megha; Nigam, A. K.

2018-04-01

In the present study magnetic and electrical transport properties of transition metal substituted Co-Ga alloys (near critical cobalt concentration) have been investigated. Analysis of temperature and field dependence of dc magnetization and ac susceptibility (ACS) data suggests an evidence of reentrant spin glass (RSG) phase in Co55.5TM3Ga41.5 (TM = Co, Cr, Fe, Cu). The magnetic transition temperatures (TC and Tf) are found to depend on the nature of TM element substitution with the exchange coupling strength Co-Fe > Co-Co > Co-Cu > Co-Cr. From magnetization dynamics precise transition temperatures for the glassy phases are estimated. It is found that characteristic relaxation times are higher than that of spin glasses with minimal spin-cluster formation. The RSG behavior has been further supported by the temperature dependence of magnetotransport studies. From the magnetic field and substitution effects it has been established that the magnetic and electrical transport properties are correlated in this system.

A Second Glass Transition in Pressure Collapsed Type II Clathrate Hydrates.

Science.gov (United States)

Andersson, Ove; Häussermann, Ulrich

2018-04-19

Type II clathrate hydrates (CHs) M·17 H 2 O, with M = tetrahydrofuran (THF) or 1,3-dioxolane, are known to collapse, or amorphize, on pressurization to ∼1.3 GPa in the temperature range 77-140 K. On heating at 1 GPa, these pressure-amorphized CH states show a weak, stretched sigmoid-shaped, heat-capacity increase because of a glass transition. Here we use thermal conductivity and heat capacity measurements to show that also type II CH with M = cyclobutanone (CB) collapses on isothermal pressurization and undergoes a similar, weak, glass transition upon heating at 1 GPa. Furthermore, we reveal for both THF CH and CB CH a second, much more pronounced, glass transition at temperatures above the thermally weak glass transition on heating in the 0.2-0.7 GPa range. This result suggests the general occurrence of two glass transitions in water-rich (94 mol %) pressure-collapsed CHs. Because of a large increase in dielectric permittivity concurrently as the weak heat capacity increase, the first glass transition must be due to kinetic unfreezing of water molecules. The thermal features of the second glass transition, measured on isobaric temperature cycling, are typical of a glass-liquid-glass transition, which suggests that pressure-amorphized CHs transform reversibly to liquids.

Re-entrant spin glass and stepped magnetization in mixed-valence SrFe3(PO4)3

International Nuclear Information System (INIS)

Shang Mingyu; Chen Yan; Tian Ge; Yuan Hongming; Feng Shouhua

2013-01-01

The 2 D channel mixed-valent iron (II/III) monophosphate SrFe 3 (PO 4 ) 3 was synthesized via one step mild hydrothermal method at 210 °C and characterized by X-ray diffraction techniques and magnetization measurements. Coexistence of antiferromagnetic superexchange and ferromagnetic superexchange interactions was supposed to be in the lattice according to the Goodenough-Kanamori-Anderson rules. Temperature dependent DC magnetization measurement shows that SrFe 3 (PO 4 ) 3 is ferrimagnet with three magnetic transitions between 2 and 350 K. Through AC magnetization measurement, re-entrant spin glass was observed due to the competition between ferromagnetic and antiferromagnetic interactions. Furthermore, an interesting field induced stepped magnetization was observed in SrFe 3 (PO 4 ) 3 at 2 K with the saturation magnetization Ms=2.4 μ B /f.u. at 5 T.

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.

Spin glass behavior in nanogranular La0.25Ca0.75MnO3 manganites

International Nuclear Information System (INIS)

2UB, Universitat de Barcelona, Martí i Franquès 1, planta 3, edifici nou, 08028 Barcelona (Spain))" data-affiliation=" (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 IN2UB, Universitat de Barcelona, Martí i Franquès 1, planta 3, edifici nou, 08028 Barcelona (Spain))" >Fernández-Martínez, Antoni; 2UB, Universitat de Barcelona, Martí i Franquès 1, planta 3, edifici nou, 08028 Barcelona (Spain))" data-affiliation=" (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 IN2UB, Universitat de Barcelona, Martí i Franquès 1, planta 3, edifici nou, 08028 Barcelona (Spain))" >García-Santiago, Antoni; 2UB, Universitat de Barcelona, Martí i Franquès 1, planta 3, edifici nou, 08028 Barcelona (Spain))" data-affiliation=" (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 IN2UB, Universitat de Barcelona, Martí i Franquès 1, planta 3, edifici nou, 08028 Barcelona (Spain))" >Hernàndez, Joan Manel; Zhang, Tao

2014-01-01

The magnetic properties of two nanogranular La 0.25 Ca 0.75 MnO 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

Elementary excitations and the phase transition in the bimodal Ising spin glass model

International Nuclear Information System (INIS)

Jinuntuya, N; Poulter, J

2012-01-01

We show how the nature of the phase transition in the two-dimensional bimodal Ising spin glass model can be understood in terms of elementary excitations. Although the energy gap with the ground state is expected to be 4J in the ferromagnetic phase, a gap 2J is in fact found if the finite lattice is wound around a cylinder of odd circumference L. This 2J gap is really a finite size effect that should not occur in the thermodynamic limit of the ferromagnet. The spatial influence of the frustration must be limited and not wrap around the system if L is large enough. In essence, the absence of 2J excitations defines the ferromagnetic phase without recourse to calculating the magnetization or investigating the system response to domain wall defects. This study directly investigates the response to temperature. We also estimate the defect concentration where the phase transition to the spin glass state occurs. The value p c = 0.1045(11) is in reasonable agreement with the literature

Relaxor behavior in spin glass perovskite Sr2CoRuO6

International Nuclear Information System (INIS)

Phatak, Rohan; Sali, S.K.; Mishra, S.K.; Das, A.

2014-01-01

Dielectric properties of Sr 2 CoRuO 6 perovskite have been investigated. The compound crystallizes in monoclinic I2/c space group, with random distribution of Co and Ru ion on B site. From our previous study, we showed this compound to be magnetic spin glass with transition at 95K, and was investigated using neutron diffraction and depolarization, ac magnetization and time dependent magnetization

Replica symmetry breaking in short range spin glasses: A review of the theoretical foundations and of the numerical evidence

International Nuclear Information System (INIS)

Marinari, E.; Zuliani, F.; Parisi, G.; Ricci-Tersenghi, F.; Ruiz-Lorenzo, J.J.

2000-04-01

We discuss Replica Symmetry Breaking (RSB) in Spin Glasses. We present an update about the state of the matter, both from the analytical and from the numerical point of view. We put a particular attention in discussing the difficulties stressed by Newman and Stein concerning the problem of constructing pure states in spin glass systems. We mainly discuss about what happens in finite dimensional, realistic spin glasses. Together with a detailed review of some of most important features, facts, data, phenomena, we present some new theoretical ideas and numerical results. We discuss among others the basic idea of the RSB theory, correlation functions, interfaces, overlaps, pure states, random field and the dynamical approach. We present new numerical results for the behavior of coupled replicas and about the numerical verification of sum rules, and we review some of the available numerical results that we consider of larger importance (for example the determination of the phase transition point, the correlation functions, the window overlaps, the dynamical behavior of the system). (author)

Electron spin resonance studies of iron-group impurities in beryllium fluoride glasses

Energy Technology Data Exchange (ETDEWEB)

Griscom, D L; Stapelbroek, M [Naval Research Lab., Washington, DC (USA); Weber, M J [California Univ., Livermore (USA). Lawrence Livermore National Lab.

1980-11-01

Electron spin resonance investigations have been carried out on unirradiated BeF/sub 2/ glasses. Two relatively intense resonances were observed in a water-free distilled glass known to contain 49 ppM Ni, 13 ppM Mn, and < 20 ppM Fe. One of these was the paramagnetic resonance spectrum of Mn/sup 2 +/. Analysis of the observed /sup 19/F superhyperfine structure demonstrated this manganese to occupy distorted octahedral sites in the glass network. The second resonance was shown by temperature and frequency dependence studies, coupled with computer line shape analysis, to be a ferromagnetic resonance signal due to precipitated ferrite phases. The data suggest that these ferrites are somewhat heterogeneous and most likely comprize magnetite-like phases similar to NiFe/sub 2/O/sub 4/. An optical extinction curve rising into the ultraviolet with an approximate lambda/sup -4/ dependence is tentatively ascribed to light scattering by ferrite particles approximately 1000 Angstroems in diameter.

Study of thermal spin crossover in [Fe(II)(isoxazole)(6)](BF4)(2) with Mossbauer spectroscopy

NARCIS (Netherlands)

Bhattacharjee, A.; van Koningsbruggen, P. J.; Hibbs, W.; Miller, Joel S.; Guetlich, P.

2007-01-01

Fe-57 Mossbauer spectroscopy of the mononuclear [Fe( II)( isoxazole)(6)]( BF4)(2) compound has been studied to reveal the thermal spin crossover of Fe( II) between low- spin ( S = 0) and high- spin ( S = 2) states. A temperature-dependent spin transition curve has been constructed with the least-

Dynamical TAP equations for non-equilibrium Ising spin glasses

DEFF Research Database (Denmark)

Roudi, Yasser; Hertz, John

2011-01-01

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...... 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...... of the magnetizations. Numerical simulations suggest that the TAP equations become exact for large systems....

Probing the chemistry of adhesion between a 316L substrate and spin-on-glass coating

DEFF Research Database (Denmark)

Lampert, Felix; Kadkhodazadeh, Shima; Kasama, Takeshi

2018-01-01

Hydrogen silsesquioxane ([HSiO3/2]n) based "spin-on-glass" has been deposited on 316L substrate and cured in Ar/H2 gas atmosphere at 600 ºC to form a continuous surface coating with sub-micrometer thickness. The coating functionality depends primarily on the adhesion to the substrate, which...... is largely affected by the chemical interaction at the interface between the coating and the substrate. We have investigated this interface by transmission electron microscopy and electron energy loss spectroscopy. The analysis identified a 5-10 nm thick interaction zone containing signals from O, Si, Cr....... In agreement with computational thermodynamics, it is proposed that the spin-on-glass forms a chemically bonded silicate-rich interaction zone with the substrate. It was further suggested that this zone is composed of a corundum-type oxide at the substrate surface, followed by an olivine-structure intermediate...

Vortex-glass transition in three dimensions

International Nuclear Information System (INIS)

Reger, J.D.; Tokuyasu, T.A.; Young, A.P.; Fisher, M.P.A.

1991-01-01

We investigate the possibility of a vortex-glass transition in a disordered type-II superconductor in a magnetic field in three dimensions by numerical studies of a simplified model. Monte Carlo simulations at finite temperature and domain-wall renormalization-group calculations at T=0 indicate that d=3 is just above the lower critical dimension d l , though the possibility that d l =3 cannot be definitely ruled out. A comparison is made with XY and Ising spin glasses. The (effective) correlation-length exponent ν and dynamical exponent z are in fairly good agreement with experiment

Lateral-access Class II restoration using resin-modified glass-ionomer or silver-cermet cement.

Science.gov (United States)

Croll, T P

1995-02-01

Direct-access preparation of a carious proximal surface is perhaps the most conservative approach to restoration. Physical properties and handling characteristics of silver amalgam and of resin composite and lack of fluoride ion release make these materials unsuitable for direct buccal- or lingual-access proximal restoration. Insufficient strengths and radiolucency of self-hardening glass-ionomer cements preclude their use for Class II restorations. However, glass-ionomer silver-cermet cement and some resin-modified glass-ionomer materials are proving useful for non-stress-bearing Class II restorations and may have applications in preventive dentistry. This article describes lateral-access Class II restoration with modified glass-ionomer cements. Emphasis is placed on careful handling of materials, maintenance of an ideal operative field, and conservation of tooth structure.

One-loop topological expansion for spin glasses in the large connectivity limit

Science.gov (United States)

Chiara Angelini, Maria; Parisi, Giorgio; Ricci-Tersenghi, Federico

2018-01-01

We apply for the first time a new one-loop topological expansion around the Bethe solution to the spin-glass model with a field in the high connectivity limit, following the methodological scheme proposed in a recent work. The results are completely equivalent to the well-known ones, found by standard field-theoretical expansion around the fully connected model (Bray and Roberts 1980, and following works). However this method has the advantage that the starting point is the original Hamiltonian of the model, with no need to define an associated field theory, nor to know the initial values of the couplings, and the computations have a clear and simple physical meaning. Moreover this new method can also be applied in the case of zero temperature, when the Bethe model has a transition in field, contrary to the fully connected model that is always in the spin-glass phase. Sharing with finite-dimensional model the finite connectivity properties, the Bethe lattice is clearly a better starting point for an expansion with respect to the fully connected model. The present work is a first step towards the generalization of this new expansion to more difficult and interesting cases as the zero-temperature limit, where the expansion could lead to different results with respect to the standard one.

Replica analysis of partition-function zeros in spin-glass models

International Nuclear Information System (INIS)

Takahashi, Kazutaka

2011-01-01

We study the partition-function zeros in mean-field spin-glass models. We show that the replica method is useful to find the locations of zeros in a complex parameter plane. For the random energy model, we obtain the phase diagram in the plane and find that there are two types of distributions of zeros: two-dimensional distribution within a phase and one-dimensional one on a phase boundary. Phases with a two-dimensional distribution are characterized by a novel order parameter defined in the present replica analysis. We also discuss possible patterns of distributions by studying several systems.

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.

Formation and partial melting of two types of spin-cluster glass behavior in vanadate spinel

International Nuclear Information System (INIS)

Huang Yuanjie; Pi Li; Tan Shun; Zhang Yuheng; Yang Zhaorong

2012-01-01

We report the doping effect on the various properties of spinels Co 1-x Zn x V 2 O 4 (0 ≤ x ≤ 0.2). For the parent compounds, the rise in magnetization, the valley in thermal conductance, the transition from the ferromagnetic arrangement to non-collinear alignment indicated by the specific heat for the V sublattice, especially the frequency dependence of AC susceptibility around T 1 = 59 K, verify the occurrence of the transition at T 1 besides the ferrimagnetic transition at T C . The ferrimagnetic transition at T C induces the spin-cluster glass behavior and the transition at T 1 yields the new spin-cluster glass (NSCG) behavior. As the Zn 2+ -doped content increases, the above phenomena are gradually weakening to vanishing, but the glassy behavior at T C still exists for all samples. Through the fourth-order perturbation theory, we discuss the reasons for the gradual vanishing of the transition at T 1 . (paper)

Superexchange and spin-glass formation in semimagnetic semiconductors

Science.gov (United States)

Rusin, Tomasz M.

1996-05-01

The Mn-Mn superexchange interaction in semimagnetic semiconductors A1-xMnxB (where A=Zn, Cd and B=S, Se, Te) is studied within the three-level model of the band structure. We focus on the dependence of the interaction on the interion distance Jdd(r)=J0f(r). In the present work, the function f(r) is obtained analytically. This, only weakly material-dependent function is found to decrease with Mn-Mn distance much slower than its Gaussian approximation derived previously. The exact form of the decay of the superexchange can be approximated by a power law J0r-8.5. This is close to an experimental result, J0r-6.8, determined on the basis of the spin-glass transition temperature on the composition.

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.

Quasi-realistic distribution of interaction fields leading to a variant of Ising spin glass model

International Nuclear Information System (INIS)

Tanasa, Radu; Enachescu, Cristian; Stancu, Alexandru; Linares, Jorge; Varret, Francois

2004-01-01

The distribution of interaction fields of an Ising-like system, obtained by Monte Carlo entropic sampling is used for modeling the hysteretic behavior of patterned media made of magnetic particles with a common anisotropy axis; a variant of the canonical Edwards-Anderson Ising spin glass model is introduced

On melting dynamics and the glass transition. II. Glassy dynamics as a melting process.

Science.gov (United States)

Krzakala, Florent; Zdeborová, Lenka

2011-01-21

There are deep analogies between the melting dynamics in systems with a first-order phase transition and the dynamics from equilibrium in super-cooled liquids. For a class of Ising spin models undergoing a first-order transition--namely p-spin models on the so-called Nishimori line--it can be shown that the melting dynamics can be exactly mapped to the equilibrium dynamics. In this mapping the dynamical--or mode-coupling--glass transition corresponds to the spinodal point, while the Kauzmann transition corresponds to the first-order phase transition itself. Both in mean field and finite dimensional models this mapping provides an exact realization of the random first-order theory scenario for the glass transition. The corresponding glassy phenomenology can then be understood in the framework of a standard first-order phase transition.

Quantum fluctuations in the competition among spin glass, antiferromagnetism and local pairing superconductivity

International Nuclear Information System (INIS)

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

2007-01-01

The competition among spin glass (SG), antiferromagnetism (AF) and local pairing superconductivity (PAIR) is studied in a two-sublattice fermionic Ising SG model with a local BCS pairing interaction in the presence of a transverse magnetic field Γ. The spins in different sublattices interact with Gaussian random couplings with an antiferromagnetic mean. The problem is formulated in a Grassmann path integral formalism. The static ansatz and the replica symmetry are used to obtain the half-filling thermodynamic potential. The results are shown in phase diagrams that exhibit a complex transition line separating the PAIR phase from the others. This line is second order at high temperature which ends in a tricritical point. The presence of Γ affects deeply the transition lines

Evidence for two spin-glass transitions with magnetoelastic and magnetoelectric couplings in the multiferroic (B i1 -xB ax) (F e1 -xT ix ) O3 system

Science.gov (United States)

Kumar, Arun; Kaushik, S. D.; Siruguri, V.; Pandey, Dhananjai

2018-03-01

For disordered Heisenberg systems with small single ion anisotropy (D ), two spin-glass (SG) transitions below the long-range ordered (LRO) phase transition temperature (Tc) have been predicted theoretically for compositions close to the percolation threshold. Experimental verification of these predictions is still controversial for conventional spin glasses. We show that multiferroic spin-glass systems can provide a unique platform for verifying these theoretical predictions via a study of change in magnetoelastic and magnetoelectric couplings, obtained from an analysis of diffraction data, at the spin-glass transition temperatures (TSG). Results of macroscopic (dc M (H , T ), M(t ), ac susceptibility [χ (ω, T )], and specific heat (Cp)) and microscopic (x-ray and neutron scattering) measurements are presented on disordered BiFe O3 , a canonical Heisenberg system with small single ion anisotropy, which reveal appearance of two spin-glass phases, SG1 and SG2, in coexistence with the LRO phase below the Almeida-Thouless (A-T) and Gabey-Toulouse (G-T) lines. It is shown that the temperature dependence of the integrated intensity of the antiferromagnetic (AFM) peak shows dips with respect to the Brillouin function behavior around the SG1 and SG2 transition temperatures. The temperature dependence of the unit cell volume departs from the Debye-Grüneisen behavior below the SG1 transition and the magnitude of departure increases significantly with decreasing temperature up to the electromagnon driven transition temperature below which a small change of slope occurs followed by another similar change of slope at the SG2 transition temperature. The ferroelectric polarization also changes significantly at the two spin-glass transition temperatures. These results, obtained using microscopic techniques, clearly demonstrate that the SG1 and SG2 transitions occur on the same magnetic sublattice and are intrinsic to the system. We also construct a phase diagram showing all

Structural and magnetic properties of Ni{sub 78}Fe{sub 22} thin films sandwiched between low-softening-point glasses and application in spin devices

Energy Technology Data Exchange (ETDEWEB)

Misawa, Takahiro; Mori, Sumito [Research Institute for Electronic Science, Hokkaido University, Sapporo, Hokkaido 001-0020 (Japan); Komine, Takashi [Faculty of Engineering, Ibaraki University, Hitachi, Ibaraki 316-8511 (Japan); Fujioka, Masaya; Nishii, Junji [Research Institute for Electronic Science, Hokkaido University, Sapporo, Hokkaido 001-0020 (Japan); Kaiju, Hideo, E-mail: kaiju@es.hokudai.ac.jp [Research Institute for Electronic Science, Hokkaido University, Sapporo, Hokkaido 001-0020 (Japan)

2016-12-30

Graphical abstract: This paper presents the first demonstration of the formation of Ni{sub 78}Fe{sub 22} thin films sandwiched between low-softening-point (LSP) glasses used in spin quantum cross (SQC) devices and the theoretical prediction of spin filter effect in Ni{sub 78}Fe{sub 22}-based SQC devices. The fomation of the LSP-glass/Ni{sub 78}Fe{sub 22}/LSP-glass structures was successfully demonstrated using a newly proposed thermal pressing technique. Interestingly, this technique gives rise to both a highly-oriented crystal growth in Ni{sub 78}Fe{sub 22} thin films and a 100-fold enhancement in coercivity, in contrast to those of as-deposited Ni{sub 78}Fe{sub 22} thin films. This remarkable increase in coercivity can be explained by the calculation based on two-dimensional random anisotropy model. These excellent features on structural and magnetic properties allowed us to achieve that the stray magnetic field was uniformly generated from the Ni{sub 78}Fe{sub 22} thin-film edge in the direction perpendicular to the cross section of the LSP-glass/Ni{sub 78}Fe{sub 22}/LSP-glass structures. As we calculated the stray magnetic field generated between the two edges of Ni{sub 78}Fe{sub 22} thin-film electrodes in SQC devices, a high stray field of approximately 5 kOe was generated when the gap distance between two edges of the Ni{sub 78}Fe{sub 22} thin-film electrodes was less than 5 nm and the thickness of Ni{sub 78}Fe{sub 22} was greater than 20 nm. These experimental and calculated results suggest that Ni{sub 78}Fe{sub 22} thin films sandwiched between LSP glasses can be used as electrodes in SQC devices, providing a spin-filter effect, and also our proposed techniques utilizing magnetic thin-film edges will open up new opportunities for the creation of high performance spin devices, such as large magnetoresistance devices and nanoscale spin injectors. Our paper is of strong interest to the broad audience of Applied Surface Science, as it demonstrates that the

Magnetic structures of (Co2-xNix)(OH)PO4 (x = 0.1,0.3) spin glass-like state in antiferromagnetically ordered phases

International Nuclear Information System (INIS)

Pedro, I de; Rojo, J M; Pizarro, J L; Fernandez, J RodrIguez; Marcos, J Sanchez; Fernandez-DIaz, M T; Arriortua, M I; Rojo, T

2006-01-01

Compounds of the general formula Co 2-x Ni x (OH)PO 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 1.9 Ni 0.1 (OH)PO 4 and Co 1.7 Ni 0.3 (OH)PO 4 , respectively. Specific heat data present peaks at 68 and 61 K for Co 1.9 Ni 0.1 and Co 1.7 Ni 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 2-x Ni x (OH)PO 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 N ∼70 K for Co 1.9 Ni 0.1 and ∼64 K for Co 1.7 Ni 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

A spin-frustrated cobalt(II) carbonate pyrochlore network.

Science.gov (United States)

Zheng, Yanzhen; Ellern, Arkady; Kögerler, Paul

2011-11-01

The crystal structure of the cobalt(II) carbonate-based compound cobalt(II) dicarbonate trisodium chloride, Co(CO(3))(2)Na(3)Cl, grown from a water-ethanol mixture, exhibits a three-dimensional network of corner-sharing {Co(4)(μ(3)-CO(3))(4)} tetrahedral building blocks, in which the Co(II) centres define a pyrochlore lattice and reside in a slightly distorted octahedral Co(O-CO(2))(6) environment. The space outside the hexagonal framework defined by these interlinked groups is occupied by Na(+) and Cl(-) ions. Antiferromagnetic coupling between adjacent Co(II) centres, mediated by carbonate bridges, results in geometric spin frustration which is typical for pyrochlore networks. The Co and Cl atoms reside on the special position 3, one Na atom on position 2 and a carbonate C atom on position 3.

Electric resistivity of Y (Fe1-xAlx)2 compounds in the spin glass region (0,10

International Nuclear Information System (INIS)

Souza, G.P. de.

1985-01-01

Measurements of electric resistivity in function of the temperature (1.5 1-x Al x2 pseudobinary intermetallic compounds in the region of concentration where there is a spin-glass behaviour, were carried out. The obtained results distinguished two behaviours. In certain cocentration, the minimum of resistivity at low temperatures was observed and in the others, a decrease of resistivity with increase of temperature up to environment temperature was found out. Magnetometry measurements, were carried out aiming to determine freezing critical temperature and of the order of long range, making possible to obtain more accurate measurements in the temperature range where the spin-glass, ferromagnetic and paramagnetic states occur in the compounds. (M.C.K.) [pt

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

International Nuclear Information System (INIS)

Dominguez, Miguel; Rosales, Pedro; Torres, Alfonso; Moreno, Mario; Orduña, Abdu

2012-01-01

In this work, we study the dilution of Spin-On Glass (SOG) in order to obtain high quality SiO 2 films at 200 °C, with optical and electrical characteristics similar to those of the thermally grown SiO 2 . For the production of SiO 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 −1 ), O-H (3490 cm −1 ) and C-H, C-O bonds (1139 cm −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 2 . Our results suggest that the film produced from SOG diluted with DI and cured at 200 °C is an excellent candidate to be used as insulator on flexible and large-area electronics. - Highlights: ► Preparation of high quality silicon oxide (SiO 2 ) films at 200 °C. ► Dilution of Spin-On Glass (SOG) solution was studied. ► Dilution of SOG is necessary to obtain high quality films annealed at 200 °C. ► n and k are close to those of the thermally grown SiO 2 .

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

International Nuclear Information System (INIS)

Surungan, Tasrief

2016-01-01

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. (paper)

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.

Spin-glass-like behaviour in IrSr2RECu2O8 (RE=Sm and Eu)

International Nuclear Information System (INIS)

Santos-Garcia, A.J. dos; Duijn, J. van; Alario-Franco, M.A.

2008-01-01

We report the results of magnetic and specific heat measurements on the 1212-type compounds IrSr 2 RECu 2 O 8 with RE=Sm and Eu, prepared by high-pressure and high-temperature synthesis. The magnetic susceptibility of these compounds shows a large difference in the temperature dependence of the magnetization measured under zero-field-cooled and field-cooled conditions below 87 and 71 K, respectively, and upon further cooling below ∼10 K substantial maxima are observed too. Further AC susceptibility measurements support a glassy behaviour in lower magnetic transitions whereas the specific heat measurements do not show the typical long-range ordering commonly displayed in ferro, ferri or antiferromagnetic transitions. Hysteresis loops suggest the presence of magnetic clusters in the otherwise paramagnetic zone, indicating that these compounds probably display a reentrant spin-glass transition. Results are presented and discussed. - Graphical abstract: IrSr 2 RECu 2 O 8 with RE=Sm and Eu were prepared by high-pressure and high-temperature synthesis. Both samples adopt a M-1212-type perovskite structure and a microdomain texturing of the long c-axis is observed by TEM. A very interesting magnetic behaviour is observed in these materials. A 'cluster by cluster freezing' model is proposed, instead of the classical individual spin freezing one to explain the spin-glass-like behaviour that seems to coexist with weak ferromagnetism in both compounds

Possible ergodic-nonergodic regions in the quantum Sherrington-Kirkpatrick spin glass model and quantum annealing

Science.gov (United States)

Mukherjee, Sudip; Rajak, Atanu; Chakrabarti, Bikas K.

2018-02-01

We explore the behavior of the order parameter distribution of the quantum Sherrington-Kirkpatrick model in the spin glass phase using Monte Carlo technique for the effective Suzuki-Trotter Hamiltonian at finite temperatures and that at zero temperature obtained using the exact diagonalization method. Our numerical results indicate the existence of a low- but finite-temperature quantum-fluctuation-dominated ergodic region along with the classical fluctuation-dominated high-temperature nonergodic region in the spin glass phase of the model. In the ergodic region, the order parameter distribution gets narrower around the most probable value of the order parameter as the system size increases. In the other region, the Parisi order distribution function has nonvanishing value everywhere in the thermodynamic limit, indicating nonergodicity. We also show that the average annealing time for convergence (to a low-energy level of the model, within a small error range) becomes system size independent for annealing down through the (quantum-fluctuation-dominated) ergodic region. It becomes strongly system size dependent for annealing through the nonergodic region. Possible finite-size scaling-type behavior for the extent of the ergodic region is also addressed.

Spin-glass-like dynamics of ferromagnetic clusters in La0.75Ba0.25CoO3

International Nuclear Information System (INIS)

Kumar, Devendra

2014-01-01

We report a magnetization study of the compound La 0.75 Ba 0.25 CoO 3 where the Ba 2+ doping is just above the critical limit for percolation of ferromagnetic clusters. The field cooled and zero-field cooled (ZFC) magnetization exhibit thermomagnetic irreversibility and the ac susceptibility shows a frequency dependent peak at the ferromagnetic ordering temperature (T C  ≈ 203 K) of the clusters. These features indicate the presence of a non-equilibrium state below T C . For the non-equilibrium state, the dynamic scaling of the imaginary part of the ac susceptibility and the static scaling of the nonlinear susceptibility clearly establish a spin-glass-like cooperative freezing of ferromagnetic clusters at 200.9(2) K. The assertion of the occurrence of spin-glass-like freezing of ferromagnetic clusters is further substantiated by ZFC ageing and memory experiments. We also observe certain dynamical features which are not present in a typical spin glass, such as: the initial magnetization after ZFC ageing first increases and then decreases with the waiting time; and there is an imperfect recovery of relaxation in negative temperature cycling experiments. This imperfect recovery transforms to perfect recovery for concurrent field cycling. Our analysis suggests that these additional dynamical features have their origin in the inter-cluster exchange interaction and cluster size distribution. The inter-cluster exchange interaction above the magnetic percolation level gives a superferromagnetic state in some granular thin films, but our results show the absence of a typical superferromagnetic-like state in La 0.75 Ba 0.25 CoO 3 . (paper)

Noise as a Probe of Ising Spin Glass Transitions

Science.gov (United States)

Chen, Zhi; Yu, Clare

2009-03-01

Noise is ubiquitous and and is often viewed as a nuisance. However, we propose that noise can be used as a probe of the fluctuations of microscopic entities, especially in the vicinity of a phase transition. In recent work we have used simulations to show that the noise increases in the vicinity of phase transitions of ordered systems. We have recently turned our attention to noise near the phase transitions of disordered systems. In particular, we are studying the noise near Ising spin glass transitions using Monte Carlo simulations. We monitor the system as a function of temperature. At each temperature, we obtain the time series of quantities characterizing the properties of the system, i.e., the energy and magnetization. We look at different quantities, such as the noise power spectrum and the second spectrum of the noise, to analyze the fluctuations.

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

International Nuclear Information System (INIS)

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

2011-01-01

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.

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

International Nuclear Information System (INIS)

Mishra, Utkarsh; Rakshit, Debraj; Prabhu, R; Sen, Aditi; Sen, Ujjwal

2016-01-01

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. (paper)

Comparison of high-field Moessbauer and μSR investigations on spin glasses

International Nuclear Information System (INIS)

Bogner, J.; Reissner, M.; Steiner, W.; Cywinski, R.; Dann, J.A.; Telling, M.T.F.

2001-01-01

We report on the analysis of μSR and Moessbauer measurements of the metallic spin glasses Y(Fe 0.65 Al 0.35 ) 2 and Y(Fe 0.4 Al 0.6 ) 2 above the freezing temperature (T f ) in terms of a model taking into account a dynamical process of stochastic formation and decay of magnetically correlated regions. By this model a comparison of the autocorrelation function determined by the two different measuring techniques is possible. For the temperature dependence of the autocorrelation time we find fair agreement between both experiments for T>2T f

Differential saturation study of radial and angular modulation mechanisms of electron spin--lattice relaxation for trapped hydrogen atoms in sulfuric acid glasses. [X radiation

Energy Technology Data Exchange (ETDEWEB)

Plonka, A; Kevan, L

1976-11-01

A differential ESR saturation study of allowed transitions and forbidden proton spin-flip satellite transitions for trapped hydrogen atoms in sulfuric acid glasses indicates that angular modulation dominates the spin-lattice relaxation mechanisms and suggests that the modulation arises from motion of the H atom.

NMR determination of the order parameter in proton and deuteron glasses

International Nuclear Information System (INIS)

Blinc, R.; Dolinsek, J.; Zalar, B.

1989-01-01

The inhomogeneous broadening of the ND + deuteron, O-D--O deuteron and 87 Rb quadrapole perturbed NMR spectra in Rb 0.56 (ND 4 ) 0.44 D 2 PO 4 is used for a direct determination of the Edwards-Anderson pseudo-spin glass order parameter. The data provide strong support for a model where the basic difference between magnetic spin glasses and proton or deuteron glasses is the presence of an inherent random field resulting from substitutional disorder which linearly couples to the O-D--O pseudo spins. In these systems we do not deal with a transition from a paraelectric to a pseudo-spin glass phase but rather with a transition from an ergodic pseudo-spin glass phase with a single order parameter q to a non-ergodic pseudo-spin glass phase with an infinite number of order parameters. (author). 11 refs.; 6 figs

Doping of ZnO nanowires using phosphorus diffusion from a spin-on doped glass source

International Nuclear Information System (INIS)

Bocheux, A.; Robin, I. C.; Bonaimé, J.; Hyot, B.; Feuillet, G.; Kolobov, A. V.; Fons, P.; Mitrofanov, K. V.; Tominaga, J.; Tamenori, Y.

2014-01-01

In this article, we report on ZnO nanowires that were phosphorus doped using a spin on dopant glass deposition and diffusion method. Photoluminescence measurements suggest that this process yields p-doped ZnO. The spatial location of P atoms was studied using x-ray near-edge absorption structure spectroscopy and it is concluded that the doping is amphoteric with P atoms located on both Zn and O sites

Ferromagnetism and spin glass ordering in transition metal alloys (invited)

Science.gov (United States)

Crane, S.; Carnegie, D. W., Jr.; Claus, H.

1982-03-01

Magnetic properties of transition metal alloys near the percolation threshold are often complicated by metallurgical effects. Alloys like AuFe, VFe, CuNi, RhNi, and PdNi are in general not random solid solutions but have various degrees of atomic clustering or short-range order (SRO), depending on the heat treatment. First, it is shown how the magnetic ordering temperature of these alloys varies with the degree of clustering or SRO. Second, by systematically changing this degree of clustering or SRO, important information can be obtained about the magnetic phase diagram. In all these alloys below the percolation limit, the onset of ferromagnetic order is probably preceded by a spin glass-type ordering. However, details of the magnetic phase diagram near the critical point can be quite different alloy systems.

Spin-dependent recombination processes in wide band gap II-Mn-VI compounds

International Nuclear Information System (INIS)

Godlewski, M.; Yatsunenko, S.; Khachapuridze, A.; Ivanov, V.Yu.

2004-01-01

Mechanisms of optical detection of magnetic resonance in wide band gap II-Mn-VI diluted magnetic semiconductor (DMS) are discussed based on the results of photoluminescence (PL), PL kinetics, electron spin resonance (ESR) and optically detected magnetic resonance (ODMR) and optically detected cyclotron resonance (ODCR) investigations. Spin-dependent interactions between localized spins of Mn 2+ ions and spins/magnetic moments of free, localized or bound carriers are responsible for the observed ODMR signals. We conclude that these interactions are responsible for the observed rapid shortening of the PL decay time of 4 T 1 → 6 A 1 intra-shell emission of Mn 2+ ions and also for the observed delocalization of excitons in low dimensional structures

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}.

First-order phase transition in the quantum spin glass at T=0

Energy Technology Data Exchange (ETDEWEB)

Viana, J. Roberto; Nogueira, Yamilles; Sousa, J. Ricardo de

2003-05-26

The van Hemmen model with transverse and random longitudinal field is studied to analyze the tricritical behavior in the quantum Ising spin glass at T=0. The free energy and order parameter are calculated for two types of probability distributions: Gaussian and bimodal. We obtain the phase diagram in the {omega}-H plane, where {omega} and H are the transverse and random longitudinal fields, respectively. For the case of Gaussian distribution the phase transition is of second order, while the bimodal distribution we observe second-order transition for high-transverse field and first-order transition for small transverse field, with a tricritical point in the phase diagram.

First-order phase transition in the quantum spin glass at T=0

International Nuclear Information System (INIS)

Viana, J. Roberto; Nogueira, Yamilles; Sousa, J. Ricardo de

2003-01-01

The van Hemmen model with transverse and random longitudinal field is studied to analyze the tricritical behavior in the quantum Ising spin glass at T=0. The free energy and order parameter are calculated for two types of probability distributions: Gaussian and bimodal. We obtain the phase diagram in the Ω-H plane, where Ω and H are the transverse and random longitudinal fields, respectively. For the case of Gaussian distribution the phase transition is of second order, while the bimodal distribution we observe second-order transition for high-transverse field and first-order transition for small transverse field, with a tricritical point in the phase diagram

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

Energy Technology Data Exchange (ETDEWEB)

Surungan, Tasrief, E-mail: tasrief@unhas.ac.id; Bansawang, B.J.; Tahir, Dahlang [Department of Physics, Hasanuddin University, Makassar, South Sulawesi 90245 (Indonesia)

2016-03-11

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.

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

International Nuclear Information System (INIS)

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

2016-01-01

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.

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.

Chiral-glass transition in a diluted dipolar-interaction Heisenberg system

International Nuclear Information System (INIS)

Zhang Kaicheng; Liu Guibin; Zhu Yan

2011-01-01

Recently, numerical simulations reveal that a spin-glass transition can occur in the three-dimensional diluted dipolar system. By defining the chirality of triple spins in a diluted dipolar Heisenberg spin glass, we study the chiral ordering in the system using parallel tempering algorithm and heat bath method. The finite-size scaling analysis reveals that the system undergoes a chiral-glass transition at finite temperature. - Highlights: → We define the chirality in a diluted dipolar Heisenberg system. → The system undergoes a chiral-glass transition at finite temperature. → We extract the critical exponents of the chiral-glass transition.

Electrical resistivity of Y(Fe1-x Alx)2 in the spin glass concentration range

International Nuclear Information System (INIS)

Cunha, S.F. da; Souza, G.P. de; Takeushi, A.Y.

1986-01-01

The temperature dependence of the electrical resistivity of the Y(Fe 1-x Al x ) 2 system (0.125 ≤ x ≤ 0.25) was measured. This system exhibits a minimum at low temperatures for the concentration range where the phase diagram presents a spin glass-ferromagnetic transition. A negative temperature coefficient is observed at high temperatures for x > 0.18 and was attributed to the high value of the electrical resistivity in this concentration range. (Author) [pt

Size effect in the spin glass magnetization of thin AuFe films as studied by polarized neutron reflectometry.

Science.gov (United States)

Saoudi, M; Fritzsche, H; Nieuwenhuys, G J; Hesselberth, M B S

2008-02-08

We used polarized neutron reflectometry to determine the temperature dependence of the magnetization of thin AuFe films with 3% Fe concentration. We performed the measurements in a large magnetic field of 6 T in a temperature range from 295 to 2 K. For the films in the thickness range from 500 to 20 nm we observed a Brillouin-type behavior from 295 K down to 50 K and a constant magnetization of about 0.9 micro(B) per Fe atom below 30 K. However, for the 10 nm thick film we observed a Brillouin-type behavior down to 20 K and a constant magnetization of about 1.3 micro(B) per Fe atom below 20 K. These experiments are the first to show a finite-size effect in the magnetization of single spin-glass films in large magnetic fields. Furthermore, the ability to measure the deviation from the paramagnetic behavior enables us to prove the existence of the spin-glass state where other methods relying on a cusp-type behavior fail.

Magnetic and magnetocaloric properties of spin-glass material DyNi{sub 0.67}Si{sub 1.34}

Energy Technology Data Exchange (ETDEWEB)

Chen, X. [The Ames Laboratory, U.S. Department of Energy, Iowa State University, Ames, IA 50011-3020 (United States); College of Physics and Electronic Information Engineering, Neijiang Normal University, Neijiang 641100 (China); Mudryk, Y., E-mail: slavkomk@ameslab.gov [The Ames Laboratory, U.S. Department of Energy, Iowa State University, Ames, IA 50011-3020 (United States); Pathak, A.K.; Feng, W. [The Ames Laboratory, U.S. Department of Energy, Iowa State University, Ames, IA 50011-3020 (United States); Pecharsky, V.K. [The Ames Laboratory, U.S. Department of Energy, Iowa State University, Ames, IA 50011-3020 (United States); Department of Materials Science and Engineering, Iowa State University, Ames, IA 50011-2300 (United States)

2017-08-15

Highlights: • Spin-glass state is observed in the DyNi{sub 0.67}Si{sub 1.4} compound. • Random Ni/Si distribution in the AlB{sub 2}-type structure leads to magnetic frustration. • Magnetic frustration affects magnetic field dependence of magnetocaloric effect. - Abstract: Structural, magnetic, and magnetocaloric properties of DyNi{sub 0.67}Si{sub 1.34} were investigated using X-ray powder diffraction, magnetic susceptibility, and magnetization measurements. X-ray powder diffraction pattern shows that DyNi{sub 0.67}Si{sub 1.34} crystallizes in the AlB{sub 2}-type hexagonal structure (space group: P6/mmm, No. 191, a = b = 3.9873(9) Å, and c = 3.9733(1) Å). The compound is a spin-glass with the freezing temperature T{sub G} = 6.2 K. The ac magnetic susceptibility measurements confirm magnetic frustration in DyNi{sub 0.67}Si{sub 1.34}. The maximum value of the magnetic entropy change determined from M(H) data is −16.1 J/kg K at 10.5 K for a field change of 70 kOe.

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.

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

International Nuclear Information System (INIS)

De Sanctis, Luca; Barra, Adriano; Folli, Viola

2008-01-01

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

Muon spin relaxation in random spin systems

International Nuclear Information System (INIS)

Toshimitsu Yamazaki

1981-01-01

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

Untangling complex networks: risk minimization in financial markets through accessible spin glass ground states.

Science.gov (United States)

Lisewski, Andreas Martin; Lichtarge, Olivier

2010-08-15

Recurrent international financial crises inflict significant damage to societies and stress the need for mechanisms or strategies to control risk and tamper market uncertainties. Unfortunately, the complex network of market interactions often confounds rational approaches to optimize financial risks. Here we show that investors can overcome this complexity and globally minimize risk in portfolio models for any given expected return, provided the relative margin requirement remains below a critical, empirically measurable value. In practice, for markets with centrally regulated margin requirements, a rational stabilization strategy would be keeping margins small enough. This result follows from ground states of the random field spin glass Ising model that can be calculated exactly through convex optimization when relative spin coupling is limited by the norm of the network's Laplacian matrix. In that regime, this novel approach is robust to noise in empirical data and may be also broadly relevant to complex networks with frustrated interactions that are studied throughout scientific fields.

Untangling complex networks: Risk minimization in financial markets through accessible spin glass ground states

Science.gov (United States)

Lisewski, Andreas Martin; Lichtarge, Olivier

2010-08-01

Recurrent international financial crises inflict significant damage to societies and stress the need for mechanisms or strategies to control risk and tamper market uncertainties. Unfortunately, the complex network of market interactions often confounds rational approaches to optimize financial risks. Here we show that investors can overcome this complexity and globally minimize risk in portfolio models for any given expected return, provided the margin requirement remains below a critical, empirically measurable value. In practice, for markets with centrally regulated margin requirements, a rational stabilization strategy would be keeping margins small enough. This result follows from ground states of the random field spin glass Ising model that can be calculated exactly through convex optimization when relative spin coupling is limited by the norm of the network’s Laplacian matrix. In that regime, this novel approach is robust to noise in empirical data and may be also broadly relevant to complex networks with frustrated interactions that are studied throughout scientific fields.

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.

Electron spin resonance and electron spin echo modulation studies of Cu(II) ions in the aluminosilicate chabazite: A comparison of Cu(II) cation location and adsorbate interaction with isostructural silicoaluminophosphate-34

International Nuclear Information System (INIS)

Zamadics, M.; Kevan, L.

1992-01-01

This study focuses on Cu(II) ions exchanged in the aluminosilicate zeolite chabazite. The various Cu(II) species formed after dehydration, rehydration, and exposure to adsorbates are characterized by electron spin resonance and electron spin echo modulation spectroscopies. These results are interpreted in terms of Cu(II) ion location and adsorbate interaction. The results of this study are compared to the results found earlier for SAPO-34, chabazite's structural analog from the silicoaluminophosphate group. In a hydrated sample of chabazite the Cu(II) ions are found to be in a near octahedral environment coordinated to three nonequivalent water molecules and three framework oxygens. The most probable location of the Cu(II) ion in a hydrated sample is above the plane of the six-membered ring slightly displaced into the ellipsoidal cavity. A somewhat similar location and coordination is found for Cu(II) ions in H-SAPO-34. A feature common to both CuH-chabazite and CuH-SAPO-34 is the generation of two distinct Cu(II) species upon dehydration. It is found that Cu(II) cations in chabazite interact with the various adsorbate molecules in a similar manner as Cu(II) cation in H-chabazite and three molecules of ethanol and three propanol molecules. Only the Cu(II) ions located in the hexagonal rings after dehydration were found to complex with ethylene. The differences observed in the interaction of the Cu(II) in with water, propanol, and ehtylene between SAPO-34 and chabazite can be related to the differing cation densities of these two materials. 32 refs., 7 figs., 21 tabs

Electron spin echo study of the E'-center phase relaxation in γ-irradiated quartz glass

International Nuclear Information System (INIS)

Dudkin, V.I.; Petrun'kin, V.Yu.; Rubinov, S.V.; Uspenskij, L.I.

1986-01-01

Experimental studies of phase relaxation of E'-centres in γ-irradiated quartz glass are conducted by the method of electron spin echo (ESE) for different concentrations of paramagnetic centres. Contribution of mechanisms of spectral and prompt diffusion to kinetics of amplitude drop of echo signal is proved to reduce with growth of delay time between exciting microwave pulse that results in increase of phase memory time at large delays. The mentioned property can be used in electric controlled delay lines on the base of ESE

Superconductivity and spin fluctuations in M-Zr metallic glasses (M = Cu, Ni, Co, and Fe)

International Nuclear Information System (INIS)

Altounian, Z.; Strom-Olsen, J.O.

1983-01-01

The superconducting transition temperature, upper critical field, and magnetic susceptibility have been measured in four binary metallic glass systems: Cu-Zr, Ni-Zr, Co-Zr, and Fe-Zr. For each alloy system, a full and continuous range of Zr-rich compositions accessible by melt spinning has been examined. For Cu-Zr, the range is 0.75>x>0.30; for Ni-Zr, 0.80>x>0.30; for Co-Zr, 0.80>x>0.48, and for Fe-Zr, 0.80>x>0.55 (x being the concentration of Zr in at. %). The results show clearly the influence of spin fluctuations in reducing the superconducting transition temperature. The data have been successfully analyzed using a modified form of the McMillan equation together with expressions for the Stoner enhanced magnetic susceptibility and the Ginsburg-Landau-Abrikosov-Gor'kov expression for the upper critical field

Structural features of spin-coated thin films of binary AsxS100−x chalcogenide glass system

International Nuclear Information System (INIS)

Cook, J.; Slang, S.; Golovchak, R.; Jain, H.; Vlcek, M.; Kovalskiy, A.

2015-01-01

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 x S 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 2 O 3 was confirmed as the composition of precipitate formed during dissolution. • Lack of As–As bonds explains the observed photostability of the thin films

Coexistence of ferromagnetism and spin glass behavior in antiferromagnetic Y2BaCuO5

International Nuclear Information System (INIS)

Zhu, Zhonghua; Gao, Daqiang; Zhang, Jing; Shi, Zhenhua; Gao, Hua; Yang, Zhaolong; Zhang, Zhipeng; Xue, Desheng

2013-01-01

Highlights: • Room temperature ferromagnetism is observed in ultrafine Y 2 BaCuO 5 particles. • The observed ferromagnetism originates from the oxygen defects. • A very interesting spin glass transition located at about 110 K is found. -- Abstract: We report the synthesis of a series of Y 2 BaCuO 5 samples by varying the annealing temperature with a citrate pyrolysis technique. X-ray diffraction patterns, scanning electron microscopy and transmission electron microscopy observation show the formation of a columnar Y 2 BaCuO 5 phase and these samples are composed of many irregular particles with different particle size. Magnetic measurements show that these samples exhibit room temperature ferromagnetism and the saturation magnetization decreases with increasing sintering temperature. Post-heating treatment under argon atmosphere can enhance the ferromagnetism greatly, suggesting that the magnetism is attributed to the surface oxygen defects. By measuring magnetization versus temperature curves after zero field cooling with various applied magnetic fields, two magnetic phase transitions located at about 11 and 110 K are revealed. The position of the peak at about 11 K is independent of the magnetic field; the other peak, however, becomes rounder and shifts to lower temperatures with increasing the magnetic field, showing a strong field dependence. In addition, the virgin magnetization curves with the measured temperature below 110 K display an S-type. These features are suggestive of an antiferromagnetic phase transition at about 11 K and a spin glass transition at about 110 K

[Interface bond and compatibility between GI-II glass/alumina composite and Vitadur alpha veneering porcelain].

Science.gov (United States)

Meng, Yukun; Chao, Yonglie; Liao, Yunmao

2002-01-01

Multiple layer techniques were commonly employed in fabricating all-ceramic restorations. Bond and compatibility between layers were vitally important for the clinical success of the restorations. The purposes of this study were to investigate the bond of the interface between the GI-II glass/alumina composite and Vitadur alpha veneering porcelain, and to study the thermal compatibility between them. Prepared a bar shaped specimen of GI-II glass/alumina composite 25 mm x 5 mm x 1 mm in size, with bottom surface pre-notched. The upper surface was veneered with Vitadur alpha veneering porcelain (0.2 mm opaque dentin and 0.6 mm dentin porcelain), then fractured and the fracture surface were examined under scanning electron microscope (SEM) and electron microprobe analyzer (EMPA) with electron beam of 10 micrometer in diameter; ten all-ceramic single crowns for an upper right central incisor were fabricated and the temperatures of thermal shock resistance were tested. SEM observation showed tight bond between the composite and the porcelain; The results of EMPA showed that penetration of Na, Al elements from glass/alumina into veneering porcelain and Si, K, Ca elements from veneering porcelain into glass/alumina occurred after sintering baking; The temperature of thermal shock resistance for anterior crowns in this study was 158 +/- 10.3 degrees C, cracks were mainly distributed in veneering porcelain with thicker layer. Chemical bond exists between the GI-II glass/alumina composite and Vitadur alpha veneering porcelain, and there is good thermal compatibility between them.

Insights into the crystal-packing effects on the spin crossover of [Fe(II)(1-bpp)](2+)-based materials.

Science.gov (United States)

Vela, Sergi; Novoa, Juan J; Ribas-Arino, Jordi

2014-12-28

Iron(II) complexes of the [Fe(II)(1-bpp2)](2+) type (1-bpp = 2,6-di(pyrazol-1-yl)pyridine) have been intensively investigated in the context of crystal engineering of switchable materials because their spin-crossover (SCO) properties dramatically depend on the counterions. Here, by means of DFT + U calculations at the molecular and solid state levels we provide a rationale for the different SCO behaviour of the BF4(-) and ClO4(-) salts of the parent complex; the former features Fe(II) complexes with a regular coordination geometry and undergoes a spin transition, whereas the Fe(II) complexes of the latter adopt a distorted structure and remain in the high-spin state at all temperatures. The different SCO behaviour of both salts can be explained on the basis of a combination of thermodynamic and kinetic effects. The shape of the SCO units at high temperature is thermodynamically controlled by the intermolecular interactions between the SCO units and counterions within the crystal. The spin trapping at low temperatures in the ClO4(-) salt, in turn, is traced back to a kinetic effect because our calculations have revealed the existence of a more stable polymorph having SCO units in their low-spin state that feature a regular structure. From the computational point of view, it is the first time that the U parameter is fine-tuned on the basis of CASPT2 calculations, thereby enabling an accurate description of the energetics of the spin transition at both molecular and solid-state levels.

Spin-Glass Transition and Giant Paramagnetism in Heavily Hole-Doped Bi2Sr2Co2Oy

Science.gov (United States)

Hsu, Hung Chang; Lee, Wei-Li; Lin, Jiunn-Yuan; Young, Ben-Li; Kung, Hsiang-Hsi; Huang, Jian; Chou, Fang Cheng

2014-02-01

Hole-doped single crystals of misfit-layered cobaltate Bi2-xPbxSr2-zCo2Oy (x = 0-0.61, y = 8.28-8.62, and z = 0.01-0.22) have been successfully grown using the optical floating-zone method. Heavier hole doping has been achieved through both Pb substitution in the Bi site and the more effective Sr vacancy formation. The Co4+ : Co3+ ratio can be raised significantly from its original ˜1 : 1 to 4.5 : 1, as confirmed by iodometric titration. A spin-glass transition temperature of Tg ˜ 70 K is confirmed by ac susceptibility measurement when the Co4+ : Co3+ ratio becomes higher than 2 : 1, presumably owing to the significantly increased probability of triangular geometrical frustration among antiferromagnetically coupled localized Co4+ spins.

Electron Spin Resonance Studies of Carbonic Anhydrase: Transition Metal Ions and Spin-Labeled Sulfonamides*

Science.gov (United States)

Taylor, June S.; Mushak, Paul; Coleman, Joseph E.

1970-01-01

Electron spin resonance (esr) spectra of Cu(II) and Co(II) carbonic anhydrase, and a spin-labeled sulfonamide complex of the Zn(II) enzyme, are reported. The coordination geometry of Cu(II) bound in the enzyme appears to have approximately axial symmetry. Esr spectra of enzyme complexes with metal-binding anions also show axial symmetry and greater covalency, in the order ethoxzolamide cyanide complex suggests the presence of two, and probably three, equivalent nitrogen ligands from the protein. Esr spectra of the Co(II) enzyme and its complexes show two types of Co(II) environment, one typical of the native enzyme and the 1:1 CN- complex, and one typical of a 2:1 CN- complex. Co(II) in the 2:1 complex appears to be low-spin and probably has a coordination number of 5. Binding of a spin-labeled sulfonamide to the active center immobilizes the free radical. The similarity of the esr spectra of spin-labeled Zn(II) and Co(II) carbonic anhydrases suggests that the conformation at the active center is similar in the two metal derivatives. PMID:4320976

Evidence for existence of spin glass state in single phase polycrystalline Gd0.99Sr0.01MnO3 through structural and magnetic properties

International Nuclear Information System (INIS)

Joy, Lija K.; Anantharaman, M.R.; Thomas, Senoy

2013-01-01

Single phase rare earth manganites have attracted scientific interest due to their interesting magnetic, electrical and structural properties. Bulk GdMnO 3 has metamagnetic features with a transition from antiferromagnetic to weak-ferromagnetic state upon cooling. Recently we have found promising magnetic behaviour when GdMnO 3 is doped with strontium. Magnetic behaviour of doped rare earth manganites in the form of Gd 1-x SrMnO 3 has attracted scientific interest due to their promising technological applications in data storage, as catalysts, as electrode materials and sensors. Irreversibility and sharp anomalies has been observed in the magnetization studies of polycrystalline Gd 0.99 Sr 0.01 MnO 3 perovskite synthesized by wet solid state reaction method. X-ray diffraction pattern of the system confirms the single phase orthorhombically distorted perovskite structure. The Field Cooled (FC) and Zero Field Cooled (ZFC) magnetization obtained as a function of temperature with external magnetic field 25Oe, 50Oe, and 200Oe showed thermal irreversibility along with a cusp below the ordering temperature indicating the appearance of spin glass state. The origin of this spin glass state is attributed to spin frustrations, due to the rare earth ions forming a deformed Kagome lattice. Under a magnetic field of 25Oe, the splitting between FC and ZFC magnetization is observed at 70K with a cusp in M ZFC at 45K and when the field is increased to 50Oe and 200Oe, the splitting becomes narrower and shows a shift in the irreversible temperature (T irr ) to lower temperatures 59K and 50K respectively. The spins are frozen in random directions due to a lack of long range magnetic interactions, when the system is cooled through its freezing temperature T f to T f . Room temperature variation of magnetization with applied field indicates the existence of ferromagnetic clusters of glass over antiferromagnetic background. Thermal irreversibility between FC and ZFC below T irr with a

Wafer-scale fabrication of glass-FEP-glass microfluidic devices for lipid bilayer experiments

NARCIS (Netherlands)

Bomer, Johan G.; Prokofyev, A.V.; van den Berg, Albert; le Gac, Severine

2014-01-01

We report a wafer-scale fabrication process for the production of glass-FEP-glass microdevices using UV-curable adhesive (NOA81) as gluing material, which is applied using a novel "spin & roll" approach. Devices are characterized for the uniformity of the gluing layer, presence of glue in the

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.

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

Spin-on-glass coatings for the generation of super-polishedsubstrates for extreme ultraviolet optics

Energy Technology Data Exchange (ETDEWEB)

Salmassi, Farhad; Naulleau, Patrick P.; Gullikson, Eric M.

2005-01-01

Substrates intended for use as extreme ultraviolet (EUV) optics have extremely stringent requirements in terms of finish. These requirements can dramatically increase the cost and fabrication time, especially when non-conventional shapes, such as toroids, are required. Here we present a spin-on-glass resist process capable of generating super-polished parts from inexpensive substrates. The method has been used to render diamond-turned substrates compatible for use as EUV optics. Toroidal diamond-turned optics with starting rms roughness in the 3.3 to 3.7 nm range have been smoothed to the 0.4 to 0.6 nm range. EUV reflectometry characterization of these optics has demonstrated reflectivities of approximately 63%.

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.

Critical and Griffiths-McCoy singularities in quantum Ising spin glasses on d -dimensional hypercubic lattices: A series expansion study

Science.gov (United States)

Singh, R. R. P.; Young, A. P.

2017-08-01

We study the ±J transverse-field Ising spin-glass model at zero temperature on d -dimensional hypercubic lattices and in the Sherrington-Kirkpatrick (SK) model, by series expansions around the strong-field limit. In the SK model and in high dimensions our calculated critical properties are in excellent agreement with the exact mean-field results, surprisingly even down to dimension d =6 , which is below the upper critical dimension of d =8 . In contrast, at lower dimensions we find a rich singular behavior consisting of critical and Griffiths-McCoy singularities. The divergence of the equal-time structure factor allows us to locate the critical coupling where the correlation length diverges, implying the onset of a thermodynamic phase transition. We find that the spin-glass susceptibility as well as various power moments of the local susceptibility become singular in the paramagnetic phase before the critical point. Griffiths-McCoy singularities are very strong in two dimensions but decrease rapidly as the dimension increases. We present evidence that high enough powers of the local susceptibility may become singular at the pure-system critical point.

Three-dimensional iron(ii) porous coordination polymer exhibiting carbon dioxide-dependent spin crossover.

Science.gov (United States)

Shin, Jong Won; Jeong, Ah Rim; Jeoung, Sungeun; Moon, Hoi Ri; Komatsumaru, Yuki; Hayami, Shinya; Moon, Dohyun; Min, Kil Sik

2018-04-24

We report a three-dimensional Fe(ii) porous coordination polymer that exhibits a spin crossover temperature change following CO2 sorption (though not N2 sorption). Furthermore, single crystals of the desolvated polymer with CO2 molecules at three different temperatures were characterised by X-ray crystallography.

Replica symmetry breaking solution for two-sublattice fermionic Ising spin glass models in a transverse field

International Nuclear Information System (INIS)

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

2007-01-01

The one-step replica symmetry breaking is used to study the competition between spin glass (SG) and antiferromagnetic order (AF) in two-sublattice fermionic Ising SG models in the presence of a transverse Γ and a parallel H magnetic fields. Inter- and intra-sublattice exchange interactions following Gaussian distributions are considered. The problem is formulated in a Grassmann path integral formalism within the static ansatz. Results show that H favors the non-ergodic mixed phase (AF+SG) and it destroys the AF. The Γ suppresses the magnetic orders, and the intra-sublattice interaction can introduce a discontinuous phase transition

Dipolar ferromagnets and glasses (invited)

International Nuclear Information System (INIS)

Rosenbaum, T.F.; Wu, W.; Ellman, B.; Yang, J.; Aeppli, G.; Reich, D.H.

1991-01-01

What is the ground state and what are the dynamics of 10 23 randomly distributed Ising spins? We have attempted to answer these questions through magnetic susceptibility, calorimetric, and neutron scattering studies of the randomly diluted dipolar-coupled Ising magnet LiHo x Y 1-x F 4 . The material is ferromagnetic for dipole concentrations at least as low as x=0.46, with a Curie temperature obeying mean-field scaling relative to that of pure LiHoF 4 . In the dilute spin limit, an x=0.045 crystal shows very unusual glassy properties characterized by decreasing barriers to relaxation as T→0. Its properties are consistent with a single low degeneracy ground state with a large gap for excitations. A slightly more concentrated x=0.167 sample, however, supports a complex ground state with no appreciable gap, in accordance with prevailing theories of spin glasses. The underlying causes of such disparate behavior are discussed in terms of random clusters as probed by neutron studies of the x=0.167 sample. In addition to tracing the evolution of the glassy and ferromagnetic states with dipole concentration, we investigate the effects of a transverse magnetic field on the Ising spin glass, LiHo 0.167 Y 0.833 F 4 . The transverse field mixes the eigenfunctions of the ground-state Ising doublet with the otherwise inaccessible excited-state levels. We observe a rapid decrease in the characteristic relaxation times, large changes in the spectral form of the relaxation, and a depression of the spin-glass transition temperature with the addition of quantum fluctuations

Triviality of the ground-state metastate in long-range Ising spin glasses in one dimension

Science.gov (United States)

Read, N.

2018-01-01

We consider the one-dimensional model of a spin glass with independent Gaussian-distributed random interactions, which have mean zero and variance 1/|i -j | 2 σ, between the spins at sites i and j for all i ≠j . It is known that, for σ >1 , there is no phase transition at any nonzero temperature in this model. We prove rigorously that, for σ >3 /2 , any translation-covariant Newman-Stein metastate for the ground states (i.e., the frequencies with which distinct ground states are observed in finite-size samples in the limit of infinite size, for given disorder) is trivial and unique. In other words, for given disorder and asymptotically at large sizes, the same ground state, or its global spin flip, is obtained (almost) always. The proof consists of two parts: One is a theorem (based on one by Newman and Stein for short-range two-dimensional models), valid for all σ >1 , that establishes triviality under a convergence hypothesis on something similar to the energies of domain walls and the other (based on older results for the one-dimensional model) establishes that the hypothesis is true for σ >3 /2 . In addition, we derive heuristic scaling arguments and rigorous exponent inequalities which tend to support the validity of the hypothesis under broader conditions. The constructions of various metastates are extended to all values σ >1 /2 . Triviality of the metastate in bond-diluted power-law models for σ >1 is proved directly.

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.

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....

Internal structure transition of spin-on glass by electron beam irradiation

International Nuclear Information System (INIS)

Araki, Makoto; Taniguchi, Jun; Sawada, Nobuo; Utsumi, Takayuki; Miyamoto, Iwao

2007-01-01

The effects of electron beam (EB) irradiation on spin-on glass (SOG) were investigated using thermal desorption spectroscopy. We were able to employ heat treatment as a 'development process', since we discovered that heat treatment breaks different bonds in SOG depending on whether it is applied before or after EB irradiation of SOG. In the case, when heat treatment was applied before EB irradiation of SOG, it was possible to break the Si-C bond at about 500 deg. C. In the case, when heat treatment was applied after EB irradiation of SOG, on the other hand, the -SiC bond could be broken at a lower temperature of about 400 deg. C. Using this difference between the two bond-breaking temperatures, it was possible to develop SOG using thermal desorption development (TDD). Moreover, the bond-breaking mechanisms revealed that the organic components in SOG play an important role in TDD. Hence, in order to determine the influence of organic components on TDD, the development characteristics of SOG samples with 10% and 15% organic contents were investigated

Influence of annealing conditions on the optical and structural properties of spin-coated As(2)S(3) chalcogenide glass thin films.

Science.gov (United States)

Song, Shanshan; Dua, Janesha; Arnold, Craig B

2010-03-15

Spin-coating of chalcogenide glass is a low-cost, scalable method to create optical grade thin films, which are ideal for visible and infrared applications. In this paper, we study the influence of annealing on optical parameters of As(2)S(3) films by examining UV-visible and infrared spectroscopy and correlating the results to changes in the physical properties associated with solvent removal. Evaporation of excess solvent results in a more highly coordinated, denser glass network with higher index and lower absorption. Depending on the annealing temperature and time, index values ranging from n = 2.1 to the bulk value (n = 2.4) can be obtained, enabling a pathway to materials optimization.

Coexistence of spin glass and superparamagnetism with ferrimagnetic order in polycrystalline spinel Co{sub 0.2}Zn{sub 0.8}Fe{sub 1.95}Ho{sub 0.05}O{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Bhowmik, R.N. [Experimental Condensed Matter Physics Dvision, Saha Institute of Nuclear Physics, Kolkata-70064 (India)]. E-mail: rnb@cmp.saha.ernet.in; Ranganathan, R. [Experimental Condensed Matter Physics Dvision, Saha Institute of Nuclear Physics, Kolkata-70064 (India)]. E-mail: ranga@cmp.saha.ernet.in; Nagarajan, R. [Tata Institute of Fundamental Research, Department of Condensed Matter Physics and Materials Science, Colaba Road, Mumbai (India)

2006-04-15

We discuss our investigation of DC magnetization, as a function of time, temperature and magnetic field, and explore some distinct magnetic behaviour in the polycrystalline spinel Co{sub 0.2}Zn{sub 0.8}Fe{sub 1.95}Ho{sub 0.05}O{sub 4}. The system is essentially to be a ferrimagnet and the ferrimagnetic order (spontaneous magnetization) is identified using Arrot plot of M(H) data. Application of some scaling laws have shown the coexistence of spin glass (SG) and superparamagnetism (SPM) with ferrimagnetic order (FIMO) at low and high temperature, respectively, in the system. The coexistence of SG and SPM with FIMO shows paramagnetic to ferrimagnetic state at T{sub C}{approx}225K and ferrimagnetic to cluster spin glass state below T{sub m}{approx}120K. The non-linear increase, without hysteresis, of M(H) data above T{sub C} indicates the existence of short range interacting clusters in the paramagnetic state. In addition, the anisotropy effect of Ho{sup 3+} has shown some interesting magnetic features, such as, spin glass of Ising nature and an unusual maximum in the thermoremanent magnetization about 180K.

Wafer-scale fabrication of glass-FEP-glass microfluidic devices for lipid bilayer experiments.

Science.gov (United States)

Bomer, Johan G; Prokofyev, Alexander V; van den Berg, Albert; Le Gac, Séverine

2014-12-07

We report a wafer-scale fabrication process for the production of glass-FEP-glass microdevices using UV-curable adhesive (NOA81) as gluing material, which is applied using a novel "spin & roll" approach. Devices are characterized for the uniformity of the gluing layer, presence of glue in the microchannels, and alignment precision. Experiments on lipid bilayers with electrophysiological recordings using a model pore-forming polypeptide are demonstrated.

Non-Fermi liquid and spin-glass behavior of the Sc1-xUxPd3 system

International Nuclear Information System (INIS)

Gajewski, D.A.; Allenspach, P.; Seaman, C.L.; Maple, M.B.

1994-01-01

Previous electrical resistivity ρ(T), magnetic susceptibility χ(T), and specific heat C(T) measurements on the Y 1-x U x Pd 3 system have revealed Kondo behavior for 0 K , where T K is the Kondo temperature: ρ(T)/ρ(0)∼1-T/(aT K ) and C(T)/T∼-(1/T K )ln T with evidence for a finite T=0 residual entropy S(0)=(R/2)ln(2). We report measurements of ρ(T), χ(T), and C(T) on the Sc 1-x U x Pd 3 system which reveal similar Kondo, non-Fermi liquid, and spin-glass behaviors. ((orig.))

Recent advances of spin crossover research

NARCIS (Netherlands)

Gutlich, P; van Koningsbruggen, PJ; Renz, F; Schonherr, T

2004-01-01

Thermal spin transition (spin crossover), one of the most fascinating dynamic electronic structure phenomena occurring in coordination compounds of third row transition metal ions, mostly of iron(II), iron(III) and cobalt(II) with critical ligand field strengths competing with the spin pairing

Correlated spin glass generated by structural disorder in the amorphous Dy6Fe74B20 alloy

Science.gov (United States)

Tejada, J.; Martinez, B.; Labarta, A.; Chudnovsky, E. M.

1991-10-01

Magnetic properties of the amorphous Dy-Fe-B alloy are studied in terms of the correlated-spin-glass approach of Chudnovsky et al.$-- Features predicted by the theory are clearly observed in the experiment. It is shown that the magnetization law may be presented in the form where it is determined by the dimensionless correlation function of structural disorder, C(y), only. The analysis of the magnetization curve allows one to distinguish between different models of disorder in amorphous solids. Experimental data on Dy-Fe-B are in favor of C=exp(-1/2y2).

Correlated spin glass generated by structural disorder in the amorphous Dy6Fe74B20 alloy

International Nuclear Information System (INIS)

Tejada, J.; Martinez, B.; Labarta, A.; Chudnovsky, E.M.

1991-01-01

Magnetic properties of the amorphous Dy-Fe-B alloy are studied in terms of the correlated-spin-glass approach of Chudnovsky et al.$---- Features predicted by the theory are clearly observed in the experiment. It is shown that the magnetization law may be presented in the form where it is determined by the dimensionless correlation function of structural disorder, C(y), only. The analysis of the magnetization curve allows one to distinguish between different models of disorder in amorphous solids. Experimental data on Dy-Fe-B are in favor of C=exp(-1/2y 2 )

Investigations on vanadium doped glasses

International Nuclear Information System (INIS)

Madhusudana Rao, P.

2013-01-01

The glass samples studied in the present work have been prepared by melt quenching technique. They were prepared by mixing and grinding together by appropriate amounts of Li 2 O - Na 2 O - B 2 O 3 doped with V 2 O 5 in an agate motor before transferring into crucible. The mixtures were heated in an electric furnace at 1225K for 20 mm. The melt was then quenched to room temperature by pouring it on plane brass plate and pressing it with another brass plate. White and yellow coloured glasses have been obtained with good optical quality and high transparency. Finally the vitreous sample were annealed for 3 hrs at 423K to relieve residual internal stress and slowly cooled to room temperature. The polished glasses have been used for XRD, FTIR analysis and for DSC report. The DSC thermo grams for all the glasses were recorded on in the temperature range 50-550℃ with a heating rate of 10℃/min. Electron spin resonance and optical absorption of 20Li 2 O - 10 Na 2 O - (70-X)B 2 O 3 doped with XV 2 O 5 glass system are studied. ESR spectra of V 4+ ions doped in the glass exhibit peak at g =1.98. Spin Hamiltonian parameters are calculated. It was found that these parameters are dependent upon alkali ion concentration in the glass and the VO +2 ion in an octahedral coordination with a tetragonal compression. The physical parameters of all glasses were also evaluated with respect to the composition

A method for making a glass supported system, such glass supported system, and the use of a glass support therefor

NARCIS (Netherlands)

Unnikrishnan, S.; Jansen, Henricus V.; Berenschot, Johan W.; Fazal, I.; Louwerse, M.C.; Mogulkoc, B.; Sanders, Remco G.P.; de Boer, Meint J.; Elwenspoek, Michael Curt

2008-01-01

The invention relates to a method for making a glass supported micro or nano system, comprising the steps of: i) providing a glass support; ii) mounting at least one system on at least one glass support; and iii) bonding the system to the glass support, such that the system is circumferentially

Manipulation of spin states in single II-VI-semiconductor quantum dots; Manipulation von Spinzustaenden in einzelnen II-VI-Halbleiter-Quantenpunkten

Energy Technology Data Exchange (ETDEWEB)

Hundt, Andreas

2007-10-09

Semiconductor quantum dots (QD) are objects on the nanometer scale, where charge carriers are confined in all three dimensions. This leads to a reduced interaction with the semiconductor lattice and to a discrete density of states. The spin state of a particle defines the polarisation of the emitted light when relaxating to an energetically lower state. Spin exchange and optical transition selection rules (conservation law for spin) define the optical control of spin states. In the examined QD in II-VI seminconductor systems the large polar character of the bindings enables to observe particle interactions by spectroscopy of the photo-luminescence (PL), making QD attractive for basic research. This work subjects in its first part single negatively charged non-magnetic QD. The odd number of carriers allows to study the latter in an unpaired state. By using polarization-resolved micro-PL spectroscopy, the spin-states of single, isolated QD can be studied reproducibly. Of special interest are exchange interactions in this few-particle system named trion. By excitation spectroscopy energetically higher states can be identified and characterized. The exchange interactions appearing here lead to state mixing and fine structure patterns in the spectra. Couplings in excited hole states show the way to the optical orientation of the resident electron spin. The spin configuration of the trion triplet state can be used to optically control the resident electron spin. Semimagnetic QD are focused in the second part of this work. The interaction with a paramagnetic environment of manganese spins leads to new magneto-optical properties of the QD. They reveal on a single dot level by line broadening due to spin fluctuations and by the giant Zeeman effect of the dot ensemble. Of special interest in this context is the influence of the reduced system dimension and the relatively larger surface of the system on the exchange mechanisms. The strong temperature dependence of the spin

Field-induced cluster spin glass and inverse symmetry breaking enhanced by frustration

Science.gov (United States)

Schmidt, M.; Zimmer, F. M.; Magalhaes, S. G.

2018-03-01

We consider a cluster disordered model to study the interplay between short- and long-range interactions in geometrically frustrated spin systems under an external magnetic field (h). In our approach, the intercluster long-range disorder (J) is analytically treated to get an effective cluster model that is computed exactly. The clusters follow a checkerboard lattice with first-neighbor (J1) and second-neighbor (J2) interactions. We find a reentrant transition from the cluster spin-glass (CSG) state to a paramagnetic (PM) phase as the temperature decreases for a certain range of h. This inverse symmetry breaking (ISB) appears as a consequence of both quenched disorder with frustration and h, that introduce a CSG state with higher entropy than the polarized PM phase. The competitive scenario introduced by antiferromagnetic (AF) short-range interactions increases the CSG state entropy, leading to continuous ISB transitions and enhancing the ISB regions, mainly in the geometrically frustrated case (J1 =J2). Remarkably, when strong AF intracluster couplings are present, field-induced CSG phases can be found. These CSG regions are strongly related to the magnetization plateaus observed in this cluster disordered system. In fact, it is found that each field-induced magnetization jump brings a CSG region. We notice that geometrical frustration, as well as cluster size, play an important role in the magnetization plateaus and, therefore, are also relevant in the field-induced glassy states. Our findings suggest that competing interactions support ISB and field-induced CSG phases in disordered cluster systems under an external magnetic field.

Broken symmetry in the mean field theory of the ising spin glass: replica way and no replica way

International Nuclear Information System (INIS)

De Dominicis, C.

1983-06-01

We review the type of symmetry breaking involved in the solution discovered by Parisi and in the static derivation of the solution first introduced via dynamics by Sompolinsky. We turn to a formulation of the problem due to Thouless, Anderson and Palmer (TAP) that put a set of equations for the magnetization. A probability law for the magnetization is then built. We consider two cases: (i) a canonical distribution which is shown to give indentical results to the Hamiltonian formulation under a weak and physical assumption and (ii) a white distribution characterized by two matrices and a response. We show what symmetry breaking is necessary to recover Sompolinsky free energy. In section III we supplement replica indices in the Hamiltonian approach by ''time'' indices ans show in particular that the analytic continuation involved in Sompolinsky's equilibrium derivation, is trying to mimick a translational symmetry breaking in ''time'' that incorporates Sompolinsky's ansatz of a long time scale sequence. In section IV we apply the same treatment to the white average approach and show that, replicas can be altogether discorded and replaced by ''time''. Finally, we briefly discuss the attribution of distinct answers for the standard spin glass order parameter depending on the physical situation: equilibrium or non equilibrium associated with canonical or white (non canonical) initial conditions and density matrices

Synthesis, spectroscopy, and hydrogen/deuterium exchange in high-spin iron(II) hydride complexes.

Science.gov (United States)

Dugan, Thomas R; Bill, Eckhard; MacLeod, K Cory; Brennessel, William W; Holland, Patrick L

2014-03-03

Very few hydride complexes are known in which the metals have a high-spin electronic configuration. We describe the characterization of several high-spin iron(II) hydride/deuteride isotopologues and their exchange reactions with one another and with H2/D2. Though the hydride/deuteride signal is not observable in NMR spectra, the choice of isotope has an influence on the chemical shifts of distant protons in the dimers through the paramagnetic isotope effect on chemical shift. This provides the first way to monitor the exchange of H and D in the bridging positions of these hydride complexes. The rate of exchange depends on the size of the supporting ligand, and this is consistent with the idea that H2/D2 exchange into the hydrides occurs through the dimeric complexes rather than through a transient monomer. The understanding of H/D exchange mechanisms in these high-spin iron hydride complexes may be relevant to postulated nitrogenase mechanisms.

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...... this model in finding relationships between the production conditions and the resulting fiber properties. For both processes, a free surface with large deformation and radiative and convective heat transfer must be taken into account. The continuous fiber drawing has been simulated successfully......, and parametric studies have been made. Several properties that characterize the process have been calculated, and the relationship between the fictive temperature and the cooling rate of the fibers has been found. The model for the discontinuous fiber spinning was brought to the limits of the commercial code...

Exactly solvable spin–glass models with ferromagnetic couplings: The spherical multi-p-spin model in a self-induced field

International Nuclear Information System (INIS)

Crisanti, Andrea; Leuzzi, Luca

2013-01-01

We report some results on the quenched disordered Spherical multi-p-Spin Model in presence of ferromagnetic couplings. In particular, we present the phase diagrams of some representative cases that schematically describe, in the mean-field approximation, the behavior of most known transitions in glassy materials, including dynamic arrest in super-cooled liquids, amorphous–amorphous transitions and spin–glass transitions. A simplified notation is introduced in order to compute systems properties in terms of an effective, self-induced, field encoding the whole ferromagnetic information

Superparamagnetism and spin-glass like state for the MnFe2O4 nano-particles synthesized by the thermal decomposition method

International Nuclear Information System (INIS)

Gao Ruorui; Zhang Yue; Yu Wei; Xiong Rui; Shi Jing

2012-01-01

MnFe 2 O 4 nano-particles with an average size of about 7 nm were synthesized by the thermal decomposition method. Based on the magnetic hysteresis loops measured at different temperatures the temperature-dependent saturation magnetization (M S ) and coercivity (H C ) are determined. It is shown that above 20 K the temperature-dependence of the M S and H C indicates the magnetic behaviors in the single-domain nano-particles, while below 20 K, the change of the M S and H C indicates the freezing of the spin-glass like state on the surfaces. By measuring the magnetization–temperature (M–T) curves under the zero-field-cooling (ZFC) and field-cooling procedures at different applied fields, superparamagnetism behavior is also studied. Even though in the ZFC M–T curves peaks can be observed below 160 K, superparamagnetism does not appear until the temperature goes above 300 K, which is related with the strong inter-particle interaction. - Highlights: ► MnFe 2 O 4 nano-particles with size of 7 nm were prepared. ► The surface spin-glass like state is frozen below 20 K. ► The peaks in ZFC magnetization–temperature curves are observed below 160 K. ► The inter-particle interaction inhibits the superparamagnetism at room temperature.

Magnetic properties of 3d-transition metal and rare earth fluoride glasses

International Nuclear Information System (INIS)

Renard, J.P.; Dupas, C.; Velu, E.; Jacobini, C.; Fonteneau, G.; Lucas, J.

1981-01-01

The ac susceptibility of fluoride glasses in the ternary systems PbF 2 -MnF 2 -FeF 3 , ThF 4 -BaF 2 -MnF 2 , ZnF 2 -BaF 2 -RF 3 (R = Dy-Ho) has been studied down to 0.3 K. The susceptibility of rare earth glasses exhibits a broad maximum strongly dependent on the measuring frequency ν while a spin glass transition with a sharp susceptibility cusp nearly independent on ν is observed in 3d-transition metal glasses. Magnetic after effects are observed below the spin freezing temperature. (orig.)

Aging, rejuvenation, and memory effects in short-range Ising spin glass: Cu_0.5Co_0.5Cl_2-FeCl3 GBIC

Science.gov (United States)

Suzuki, M.; Suzuki, I. S.

2004-03-01

Cu_0.5Co_0.5Cl_2-FeCl3 GBIC undergoes a spin glass (SG) transition at Tg (= 3.92 ± 0.11 K). The system shows a dynamic behavior that has some similarities and some significant differences compared to a 3D Ising SG.^1 Here we report on non-equilibrium aging dynamics which has been studied using zero-field cooled (ZFC) magnetization and low frequency AC magnetic susceptibility.^2 The time dependence of the relaxation rate S(t) = (1/H)dM_ZFC/dln t for the ZFC magnetization after the ZFC aging protocol, shows a peak at a characteristic time t_cr near a wait time t_w, corresponding to a crossover from quasi equilibrium dynamics to non-equilibrium. The time t_cr strongly depends on t_w, temperature, magnetic field, and the temperature shift. The rejuvenation effect is observed in both i^' and i^'' under the T-shift and H-shift procedures. The memory of the specific spin configurations imprinted during the ZFC aging protocol can be recalled when the system is re-heated at a constant heating rate. The aging, rejuvenation, and memory effects are discussed in terms of the scaling concepts derived from numerical studies on 3D Edwards-Anderson spin glass model. 1. I.S. Suzuki and M. Suzuki, Phys. Rev. B 68, 094424 (2003) 2. M. Suzuki and I.S. Suzuki, cond-mat/0308285

Kondo effect and spin-glass freezing of the magnetic impurities Cr, Mn, and Fe in superconducting palladium hydride

International Nuclear Information System (INIS)

van Dongen, J.C.M.; van Dijk, D.; Mydosh, J.A.

1981-01-01

Through low-field ac susceptibility measurements we have determined the depression of the superconducting transition temperature T/sub c/ in palladium hydride (T/sub c/0 = 9.3 K) as a function of impurity concentration x for Cr, Mn, and Fe. For Cr and Fe similar values for the initial T/sub c/ depression were found, i.e., -150 K/at. % Cr and -145 K/at. % Fe. From resistivity experiments we are able to estimate the Kondo temperatures T/sub K/, i.e., T/sub K/approx. =10 K for Cr and T/sub K/approx. =5 K for Fe. Since i.e., T/sub K/approx. =10 K for Cr and T/sub K/approx. =5 K for Fe. Since systems exhibits an enhanced pair breaking as described by the theory of Mueller-Hartmann and Zittartz. In contrast, for Mn the initial T/sub c/ depression is -21 K/at. % and T/sub K/<< T/sub c/0, as can be concluded from our resistivity measurements. This means that Mn in PdH exhibits a temperature-independent pair breaking of the Abrikosov and Gor'kov type. However, at larger Mnx values a shoulder appears in T/sub c/(x). We interpret this enhanced superconductivity, according to the theory of Soukoulis and Grest, as being due to the onset of time correlations and short-range antiferromagnetic ordering between the Mn moments. These interaction effects are a precursor to the spin-glass freezing at a lower temperature T/sub f/. Our results suggest a favorable coexistance of superconductivity with the spin-glass state

Spin-glass like behaviour in the nanoporous Fe{sub 2}O{sub 3} with amorphous structure

Energy Technology Data Exchange (ETDEWEB)

Thakur, M; Majumdar, S; Giri, S [Department of Solid State Physics and Center for Advanced Materials, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India); Bhaumik, A; Nandi, M [Department of Materials Science and Center for Advanced Materials, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India); Nakamura, H; Kobayashi, H; Kohara, T [Graduate School of Material Science, University of Hyogo, Kamigori, Ako-gun, Hyogo 678-1297 (Japan)], E-mail: sspsg2@iacs.res.in

2008-07-23

The porous Fe{sub 2}O{sub 3} was synthesized chemically. The average size of the particle was {approx}85.0 nm, which was observed by scanning electron microscopy. The signature of porous structure was confirmed by a N{sub 2} adsorption/desorption isotherm and intense x-ray powder diffraction peak at low angle. The x-ray diffraction pattern at high angle indicates the amorphous structure. Moessbauer investigations show that the value of the hyperfine field is {approx}498.0 kOe at 4.2 K which is much smaller than that of the hyperfine field of crystalline {alpha}/{gamma}-Fe{sub 2}O{sub 3} and consistent with the values of amorphous Fe{sub 2}O{sub 3}. The temperature dependence of zero-field cooled magnetization exhibits a peak at 18.0 K (T{sub f}), where T{sub f} follows the Almeida-Thouless relation as T{sub f} {proportional_to} H{sup 2/3}. The ageing phenomenon of the magnetic relaxation below T{sub f} and the memory effect in the field-cooled magnetization indicate the typical features of the classical spin-glass compounds below the spin freezing temperature at T{sub f}.

Rotational Invariance of the 2d Spin - Spin Correlation Function

Science.gov (United States)

Pinson, Haru

2012-09-01

At the critical temperature in the 2d Ising model on the square lattice, we establish the rotational invariance of the spin-spin correlation function using the asymptotics of the spin-spin correlation function along special directions (McCoy and Wu in the two dimensional Ising model. Harvard University Press, Cambridge, 1973) and the finite difference Hirota equation for which the spin-spin correlation function is shown to satisfy (Perk in Phys Lett A 79:3-5, 1980; Perk in Proceedings of III international symposium on selected topics in statistical mechanics, Dubna, August 22-26, 1984, JINR, vol II, pp 138-151, 1985).

A quantum spin system with random interactions I

Indian Academy of Sciences (India)

. In order to study the dynamics of a quantum spin glass we model it as a .... Next we construct a family of strongly continuous one-parameter groups of c-auto- morphisms which determine the evolution of the spin system. To this end, we have ...

Iron(II) and Iron(III) Spin Crossover: Toward an Optimal Density Functional

DEFF Research Database (Denmark)

Siig, Oliver S; Kepp, Kasper P.

2018-01-01

Spin crossover (SCO) plays a major role in biochemistry, catalysis, materials, and emerging technologies such as molecular electronics and sensors, and thus accurate prediction and design of SCO systems is of high priority. However, the main tool for this purpose, density functional theory (DFT......), is very sensitive to applied methodology. The most abundant SCO systems are Fe(II) and Fe(III) systems. Even with average good agreement, a functional may be significantly more accurate for Fe(II) or Fe(III) systems, preventing balanced study of SCO candidates of both types. The present work investigates....../precise, inaccurate/imprecise) are observed. More generally, our work illustrates the importance not only of overall accuracy but also of balanced accuracy for systems likely to occur in context....

Charge and Spin Transport in Spin-orbit Coupled and Topological Systems

KAUST Repository

Ndiaye, Papa Birame

2017-01-01

for next-generation technology, three classes of systems that possibly enhance the spin and charge transport efficiency: (i)- topological insulators, (ii)- spin-orbit coupled magnonic systems, (iii)- topological magnetic textures (skyrmions and 3Q magnetic

Photoluminescence and ESR of glasses of the Ge-S system

International Nuclear Information System (INIS)

Cernoskova, E.; Cernosek, Z.; Holubova, J.

1999-01-01

In this work the chalcogenide glasses were studied by photoluminescence, electron spin resonance (ESR) as well as optically induce ESR (LESR) methods. Dependence of energy of luminescence and Stokes shift on glass composition was determined

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

Muonium spin exchange in spin-polarized media: Spin-flip and -nonflip collisions

International Nuclear Information System (INIS)

Senba, M.

1994-01-01

The transverse relaxation of the muon spin in muonium due to electron spin exchange with a polarized spin-1/2 medium is investigated. Stochastic calculations, which assume that spin exchange is a Poisson process, are carried out for the case where the electron spin polarization of the medium is on the same axis as the applied field. Two precession signals of muonium observed in intermediate fields (B>30 G) are shown to have different relaxation rates which depend on the polarization of the medium. Furthermore, the precession frequencies are shifted by an amount which depends on the spin-nonflip rate. From the two relaxation rates and the frequency shift in intermediate fields, one can determine (i) the encounter rate of muonium and the paramagnetic species, (ii) the polarization of the medium, and most importantly (iii) the quantum-mechanical phase shift (and its sign) associated with the potential energy difference between electron singlet and triplet encounters. Effects of spin-nonflip collisions on spin dynamics are discussed for non-Poisson as well as Poisson processes. In unpolarized media, the time evolution of the muon spin in muonium is not influenced by spin-nonflip collisions, if the collision process is Poissonian. This seemingly obvious statement is not true anymore in non-Poissonian processes, i.e., it is necessary to specify both spin-flip and spin-nonflip rates to fully characterize spin dynamics

Spin Forming Aluminum Crew Module (CM) Metallic Aft Pressure Vessel Bulkhead (APVBH) - Phase II

Science.gov (United States)

Hoffman, Eric K.; Domack, Marcia S.; Torres, Pablo D.; McGill, Preston B.; Tayon, Wesley A.; Bennett, Jay E.; Murphy, Joseph T.

2015-01-01

The principal focus of this project was to assist the Multi-Purpose Crew Vehicle (MPCV) Program in developing a spin forming fabrication process for manufacture of the Orion crew module (CM) aft pressure vessel bulkhead. The spin forming process will enable a single piece aluminum (Al) alloy 2219 aft bulkhead resulting in the elimination of the current multiple piece welded construction, simplify CM fabrication, and lead to an enhanced design. Phase I (NASA TM-2014-218163 (1)) of this assessment explored spin forming the single-piece CM forward pressure vessel bulkhead. The Orion MPCV Program and Lockheed Martin (LM) recently made two critical decisions relative to the NESC Phase I work scope: (1) LM selected the spin forming process to manufacture a single-piece aft bulkhead for the Orion CM, and (2) the aft bulkhead will be manufactured from Al 2219. Based on the Program's new emphasis related to the spin forming process, the NESC was asked to conduct a Phase II assessment to assist in the LM manufacture of the aft bulkhead and to conduct a feasibility study into spin forming the Orion CM cone. This activity was approved on June 19, 2013. Dr. Robert Piascik, NASA Technical Fellow for Materials at the Langley Research Center (LaRC), was selected to lead this assessment. The project plan was approved by the NASA Engineering and Safety Center (NESC) Review Board (NRB) on July 18, 2013. The primary stakeholders for this assessment were the NASA and LM MPCV Program offices. Additional benefactors are commercial launch providers developing CM concepts.

Rapid spin-state interconversion in the bis-complex of tris-(1-pyrazolyl) methane with Fe(II) studied by Moessbauer spectroscopy

International Nuclear Information System (INIS)

Winkler, H.; Trautwein, A.X.; Toftlund, H.

1992-01-01

Dynamic spin equilibrium is observed in a complex of the [Fe(II)-N 6 ] type above room temperature. The Moessbauer lineshapes as function of temperature can be understood by means of the random-frequency-modulation model. Taking into accout the different Lamb-Moessbauer factors of the low- and high-spin state yields true populations of the two spin states. The transition rates follow rather well an Arrhenius law. With appropriate assumptions an activation energy ΔE LH =18(1) kJmol -1 is deduced. (orig.)

The Effect of a Glass Ceramic Insert in Sandwich Technique on Microleakage in Class II Composite Resin Restorations

Directory of Open Access Journals (Sweden)

Hila Hajizadeh

2015-06-01

Full Text Available Introduction: The aim of the present study was to evaluate the effect of glass ceramic insert in the sandwich technique to reduce microleakage in class II composite resin restorations. Methods: Sixty sound human upper second premolars were selected and randomly divided into six groups (n=10. Class II box-only cavities were prepared in distal aspects of each tooth with gingival margin located approximately 0.5 mm below the CEJ. Group A (Control was restored incrementally with Tetric Ceram and a total-etch bonding technique. Group B and C were restored with sandwich technique using a compomer (Compoglass F or flowable composite resin (Tetric Flow as the lining material at gingival floor, respectively. Group D, E and F were represented in the same way as group A, B and C and a glass ceramic insert was added to the composite bulk. The specimens were thermo-mechanically cycled, and then immersed in 0.5 % basic fuschin for 24 hours. Dye penetration was detected using a sectioning technique. Results: No significant difference was found between total-etch bonding and sandwich techniques. The placement of an insert caused an increase in   microleakage in all groups significantly (P < 0.05. Group D (no liner/ with glass insert showed the highest amount of microleakage and Group A (no liner/ without glass insert resulted in the lowest amount of total microleakage. Conclusion: Placement of glass ceramic insert could not decrease gingival leakage. According to the limitation of this study a composite resin restorations with incremental technique is recommended

Role of fluctuations in the phase transitions of coupled plaquette spin models of glasses

Directory of Open Access Journals (Sweden)

Giulio Biroli, Charlotte Rulquin, Gilles Tarjus, Marco Tarzia

2016-10-01

Full Text Available We study the role of fluctuations on the thermodynamic glassy properties of plaquette spin models, more specifically on the transition involving an overlap order parameter in the presence of an attractive coupling between different replicas of the system. We consider both short-range fluctuations associated with the local environment on Bethe lattices and long-range fluctuations that distinguish Euclidean from Bethe lattices with the same local environment. We find that the phase diagram in the temperature-coupling plane is very sensitive to the former but, at least for the $3$-dimensional (square pyramid model, appears qualitatively or semi-quantitatively unchanged by the latter. This surprising result suggests that the mean-field theory of glasses provides a reasonable account of the glassy thermodynamics of models otherwise described in terms of the kinetically constrained motion of localized defects and taken as a paradigm for the theory of dynamic facilitation. We discuss the possible implications for the dynamical behavior.

I. Advances in NMR Signal Processing. II. Spin Dynamics in Quantum Dissipative Systems

Energy Technology Data Exchange (ETDEWEB)

Lin, Yung-Ya [Univ. of California, Berkeley, CA (United States)

1998-11-01

Part I. Advances in IVMR Signal Processing. Improvements of sensitivity and resolution are two major objects in the development of NMR/MRI. A signal enhancement method is first presented which recovers signal from noise by a judicious combination of a priordmowledge to define the desired feasible solutions and a set theoretic estimation for restoring signal properties that have been lost due to noise contamination. The effect of noise can be significantly mitigated through the process of iteratively modifying the noisy data set to the smallest degree necessary so that it possesses a collection of prescribed properties and also lies closest to the original data set. A novel detection-estimation scheme is then introduced to analyze noisy and/or strongly damped or truncated FIDs. Based on exponential modeling, the number of signals is detected based on information estimated using the matrix pencil method. theory and the spectral parameters are Part II. Spin Dynamics in body dipole-coupled systems Quantum Dissipative Systems. Spin dynamics in manyconstitutes one of the most fundamental problems in magnetic resonance and condensed-matter physics. Its many-spin nature precludes any rigorous treatment. ‘Therefore, the spin-boson model is adopted to describe in the rotating frame the influence of the dipolar local fields on a tagged spin. Based on the polaronic transform and a perturbation treatment, an analytical solution is derived, suggesting the existence of self-trapped states in the. strong coupling limit, i.e., when transverse local field >> longitudinal local field. Such nonlinear phenomena originate from the joint action of the lattice fluctuations and the reaction field. Under semiclassical approximation, it is found that the main effect of the reaction field is the renormalization of the Hamiltonian of interest. Its direct consequence is the two-step relaxation process: the spin is initially localized in a quasiequilibrium state, which is later detrapped by

Shapes of tree representations of spin-glass landscapes

International Nuclear Information System (INIS)

Hordijk, Wim; Fontanari, Jose F; Stadler, Peter F

2003-01-01

Much of the information about the multi-valley structure of disordered spin systems can be convened in a simple tree structure - a barrier tree - the leaves and internal nodes of which represent, respectively, the local minima and the lowest energy saddles connecting those minima. Here we apply several statistics used in the study of phylogenetic trees to barrier trees that result from the energy landscapes of p-spin models. These statistics give information about the shape of these barrier trees, in particular about balance and symmetry. We then ask if they can be used to classify different types of landscapes, compare them with results obtained from random trees, and investigate the structure of subtrees of the barrier trees. We conclude that at least one of the used statistics is capable of distinguishing different types of landscapes, that the barrier trees from p-spin energy landscapes are quite different from random trees, and that subtrees of barrier trees do not reflect the overall tree structure, but their structure is correlated with their 'depth' in the tree

Spin injection and detection in lateral spin valves with hybrid interfaces

Science.gov (United States)

Wang, Le; Liu, Wenyu; Ying, Hao; Chen, Luchen; Lu, Zhanjie; Han, Shuo; Chen, Shanshan; Zhao, Bing; Xu, Xiaoguang; Jiang, Yong

2018-06-01

Spin injection and detection in lateral spin valves with hybrid interfaces comprising a Co/Ag transparent contact and a Co/MgO/Ag junction (III) are investigated at room temperature in comparison with pure Co/Ag transparent contacts (I) and Co/MgO/Ag junctions (II). The measured spin-accumulation signals of a type III device are five times higher than those for type I. The extracted spin diffusion length in Ag is 180 nm for all three types of devices. The enhancement of the spin signal of the hybrid structure is mainly attributed to the increase of the interfacial spin polarization from the Co/MgO/Ag junction.

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.

Real time neutron diffraction and NMR of the Empress II glass-ceramic system.

Science.gov (United States)

O'Donnell, M D; Hill, R G; Karpukhina, N; Law, R V

2011-10-01

This study reports real time neutron diffraction on the Empress II glass-ceramic system. The commercial glass-ceramics was characterized by real time neutron diffraction, ³¹P and ²⁹Si solid-state MAS-NMR, DSC and XRD. On heating, the as-received glass ceramic contained lithium disilicate (Li₂Si₂O₅), which melted with increasing temperature. This was revealed by neutron diffraction which showed the Bragg peaks for this phase had disappeared by 958°C in agreement with thermal analysis. On cooling lithium metasilicate (Li₂SiO₃) started to form at around 916°C and a minor phase of cristobalite at around 852°C. The unit cell volume of both Li-silicate phases increased linearly with temperature at a rate of +17×10⁻³ ų.°C⁻¹. Room temperature powder X-ray diffraction (XRD) of the material after cooling confirms presence of the lithium metasilicate and cristobalite as the main phases and shows, in addition, small amount of lithium disilicate and orthophosphate. ³¹P MAS-NMR reveals presence of the lithiorthophosphate (Li₃PO₄) before and after heat treatment. The melting of lithium disilicate on heating and crystallisation of lithium metasilicate on cooling agree with endothermic and exotermic features respectively observed by DSC. ²⁹Si MAS-NMR shows presence of lithium disilicate phase in the as-received glass-ceramic, though not in the major proportion, and lithium metasilicate in the material after heat treatment. Both phases have significantly long T₁ relaxation time, especially the lithium metasilicate, therefore, a quantitative analysis of the ²⁹Si MAS-NMR spectra was not attempted. Significance. The findings of the present work demonstrate importance of the commercially designed processing parameters in order to preserve desired characteristics of the material. Processing the Empress II at a rate slower than recommended 60°C min⁻¹ or long isothermal hold at the maximal processing temperature 920°C can cause

Optical properties of 3d transition metal ion-doped sodium borosilicate glass

International Nuclear Information System (INIS)

Wen, Hongli; Tanner, Peter A.

2015-01-01

Graphical abstract: Photographs of undoped (SiO 2 ) 50 (Na 2 O) 25 (B 2 O 3 ) 25 (SiNaB) glass and transition metal ion-doped (TM) 0.5 (SiO 2 ) 49.5 (Na 2 O) 25 (B 2 O 3 ) 25 glass samples. - Highlights: • 3d transition metal ion (from Ti to Zn) doped SiO 2 -Na 2 O-B 2 O 3 glasses. • Optical properties of doped glasses investigated. • V(IV,V); Cr(III, VI); Mn(II,III); Fe(II,III); Co(II); Ni(II); Cu(II) by XANES, DRS. • Strong visible absorption but only vanadium ion gives strong emission in glass. - Abstract: SiO 2 -Na 2 O-B 2 O 3 glasses doped with 3d-transition metal species from Ti to Zn were prepared by the melting-quenching technique and their optical properties were investigated. The X-ray absorption near edge spectra of V, Cr, and Mn-doped glasses indicate that the oxidation states of V(IV, V), Cr(III, VI) and Mn(II, III) exist in the studied glasses. The oxidation states revealed from the diffuse reflectance spectra of the glasses are V(IV, V), Cr(III, VI), Mn(III), Fe(II, III), Co(II), Ni(II), and Cu(II). Most of the 3d transition element ions exhibit strong absorption in the visible spectral region in the glass. Under ultraviolet excitation, the undoped sodium borosilicate glass produces weak and broad emission, while doping of vanadium introduces strong and broad emission due to the V(V) charge transfer transition. Only weak emission is observed from Ti(IV), Mn(II), Fe(III) and Cu(II), partly resulting from the strong electron–phonon coupling of the 3d-electrons and the relatively high phonon energy of the studied glass host, with the former leading to dominant nonradiative relaxation based on multiphonon processes for most of the 3d excited states

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.

Deposition of Ge{sub 23}Sb{sub 7}S{sub 70} chalcogenide glass films by electrospray

Energy Technology Data Exchange (ETDEWEB)

Novak, Spencer, E-mail: spencen@g.clemson.edu [Department of Materials Science and Engineering, COMSET, Clemson University, Clemson, SC (United States); College of Optics and Photonics, CREOL, University of Central FL (United States); Johnston, Danvers E.; Li, Cheng; Deng, Weiwei [Department of Mechanical and Aerospace Engineering, University of Central FL (United States); Richardson, Kathleen [Department of Materials Science and Engineering, COMSET, Clemson University, Clemson, SC (United States); College of Optics and Photonics, CREOL, University of Central FL (United States)

2015-08-03

Solution-based chalcogenide glass films, traditionally deposited by spin-coating, are attractive for their potential use in chip-based devices operating in the mid-infrared and for ease of nanostructure incorporation. To overcome limitations of spin-coating such as excessive material waste and difficulty for scale-up, this paper introduces electrospray as a film deposition technique for solution-based chalcogenide glasses. Electrospray is shown to produce Ge{sub 23}Sb{sub 7}S{sub 70} films with similar surface quality and optical properties as films deposited by spin-coating. The advantages of electrospray deposition for nanoparticle dispersion, scalable and continuous manufacturing with little material waste, and comparable film quality to spin-coating make electrospray a promising deposition method for practical applications of chalcogenide glass films. - Highlights: • Electrospray film deposition processing of Ge{sub 23}Sb{sub 7}S{sub 70} films was developed. • Traditional spin-coated films were also fabricated in parallel. • Optical properties and surface quality found to be similar between two approaches.

Elastic oscillation damping and magnetic susceptibility in Y19Fe81 spin glass in the temperature range 70-300 K

International Nuclear Information System (INIS)

Zolotukhin, I.V.; Balalaev, S.Yu.

1990-01-01

Relaxation properties of Y 19 Fe 81 spin glass (SG) were investigated by means of internal friction(IF). Relaxation process resulting from transition to SG state was determined at sound range frequencies in amorphous alloy. On the basis of the obtained results concerning IF and magnetic susceptibility it follows, that relaxation of certain part of cluster magnetic moments lies within 10 -5 -10 -3 s limits with 0.11±0.06 eV activation energy. IF technique is shown to be used for investigation into relaxation properties, in particular, for acquisition of data on temperature of transition to SG' state

Quantum entanglement for systems of identical bosons: II. Spin squeezing and other entanglement tests

International Nuclear Information System (INIS)

Dalton, B J; Goold, J; Garraway, B M; Reid, M D

2017-01-01

These two accompanying papers are concerned with entanglement for systems of identical massive bosons and the relationship to spin squeezing and other quantum correlation effects. The main focus is on two mode entanglement, but multi-mode entanglement is also considered. The bosons may be atoms or molecules as in cold quantum gases. The previous paper I dealt with the general features of quantum entanglement and its specific definition in the case of systems of identical bosons. Entanglement is a property shared between two (or more) quantum sub-systems. In defining entanglement for systems of identical massive particles, it was concluded that the single particle states or modes are the most appropriate choice for sub-systems that are distinguishable, that the general quantum states must comply both with the symmetrization principle and the super-selection rules (SSR) that forbid quantum superpositions of states with differing total particle number (global SSR compliance). Further, it was concluded that (in the separable states) quantum superpositions of sub-system states with differing sub-system particle number (local SSR compliance) also do not occur. The present paper II determines possible tests for entanglement based on the treatment of entanglement set out in paper I. Several inequalities involving variances and mean values of operators have been previously proposed as tests for entanglement between two sub-systems. These inequalities generally involve mode annihilation and creation operators and include the inequalities that define spin squeezing. In this paper, spin squeezing criteria for two mode systems are examined, and spin squeezing is also considered for principle spin operator components where the covariance matrix is diagonal. The proof, which is based on our SSR compliant approach shows that the presence of spin squeezing in any one of the spin components requires entanglement of the relevant pair of modes. A simple Bloch vector test for

Quantum entanglement for systems of identical bosons: II. Spin squeezing and other entanglement tests

Science.gov (United States)

Dalton, B. J.; Goold, J.; Garraway, B. M.; Reid, M. D.

2017-02-01

These two accompanying papers are concerned with entanglement for systems of identical massive bosons and the relationship to spin squeezing and other quantum correlation effects. The main focus is on two mode entanglement, but multi-mode entanglement is also considered. The bosons may be atoms or molecules as in cold quantum gases. The previous paper I dealt with the general features of quantum entanglement and its specific definition in the case of systems of identical bosons. Entanglement is a property shared between two (or more) quantum sub-systems. In defining entanglement for systems of identical massive particles, it was concluded that the single particle states or modes are the most appropriate choice for sub-systems that are distinguishable, that the general quantum states must comply both with the symmetrization principle and the super-selection rules (SSR) that forbid quantum superpositions of states with differing total particle number (global SSR compliance). Further, it was concluded that (in the separable states) quantum superpositions of sub-system states with differing sub-system particle number (local SSR compliance) also do not occur. The present paper II determines possible tests for entanglement based on the treatment of entanglement set out in paper I. Several inequalities involving variances and mean values of operators have been previously proposed as tests for entanglement between two sub-systems. These inequalities generally involve mode annihilation and creation operators and include the inequalities that define spin squeezing. In this paper, spin squeezing criteria for two mode systems are examined, and spin squeezing is also considered for principle spin operator components where the covariance matrix is diagonal. The proof, which is based on our SSR compliant approach shows that the presence of spin squeezing in any one of the spin components requires entanglement of the relevant pair of modes. A simple Bloch vector test for

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.

Spin-echo observation of radio frequency induced flux lattice annealing (RIFLA) in a type-II superconductor

International Nuclear Information System (INIS)

Clark, W.G.; Hanson, M.E.; Wong, W.H.

1999-01-01

We report the annealing of a strained flux line lattice (FLL) in 10 μm diameter type-II superconducting NbTi filaments by an RF magnetic field at 4.2 K in a magnetic field of 1 T. The strained FLL is prepared by slowly changing the direction of the applied magnetic field. When the RF magnetic field used to generate a 93 Nb NMR spin echo anneals the FLL, there is a corresponding reduction in the amplitude of the spin echo. Starting from an annealed condition, a rotation threshold of 3 mr is needed to produce enough FLL strain to be observed in these measurements. (orig.)

Spinning cylinder experiments SC-I and SC-II: A review of results and analyses provided to the FALSIRE project

International Nuclear Information System (INIS)

Morland, E.; Sherry, A.H.

1993-01-01

A series of six large-scale experiments have been carried out at AEA Technology using the Spinning Cylinder test facility. Results from two of those experiments (SC-I and SC-II) have been provided to Project FALSIRE and are reviewed in this paper. The Spinning Cylinder tests were carried out using hollow cylinders of 1.4m outer diameter, 0.2m wall thickness and 1.3m length, containing full-length axial defects and fabricated from a modified A508 Class 3 steel. The first Spinning Cylinder test (SC-I) was an investigation of stable ductile growth induced via mechanical (primary) loading and under conditions of contained yielding. Mechanical loading was provided in the hoop direction by rotating the cylinder about its major axis within an enclosed oven. The second test (SC-II) investigated stable ductile growth under severe thermal shock (secondary) loading again under conditions of contained yielding. In this case thermal shock was produced by spraying cold water on the inside surface of the heated cylinder whilst it was rotating. For each experiment, results are presented in terms of a number of variables, eg. crack growth, temperature, stress, strain and applied K and J. In addition, an overview of the analyses of the FALSIRE Phase-1 report is also presented with respect to test SC-I and SC-II. 4 refs., 14 figs., 13 tabs

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

Stretched exponential relaxation in molecular and electronic glasses

International Nuclear Information System (INIS)

Phillips, J.C.

1996-01-01

Stretched exponential relaxation, exp[-(t/τ) β ], fits many relaxation processes in disordered and quenched electronic and molecular systems, but it is widely believed that this function has no microscopic basis, especially in the case of molecular relaxation. For electronic relaxation the appearance of the stretched exponential is often described in the context of dispersive transport, where β is treated as an adjustable parameter, but in almost all cases it is generally assumed that no microscopic meaning can be assigned to 0 g , a glass transition temperature. We show that for molecular relaxation β(T g ) can be understood, providing that one separates extrinsic and intrinsic effects, and that the intrinsic effects are dominated by two magic numbers, β SR =3/5 for short-range forces, and β K =3/7 for long-range Coulomb forces, as originally observed by Kohlrausch for the decay of residual charge on a Leyden jar. Our mathematical model treats relaxation kinetics using the Lifshitz-Kac-Luttinger diffusion to traps depletion model in a configuration space of effective dimensionality, the latter being determined using axiomatic set theory and Phillips-Thorpe constraint theory. The experiments discussed include ns neutron scattering experiments, particularly those based on neutron spin echoes which measure S(Q, t) directly, and the traditional linear response measurements which span the range from μs to s, as collected and analysed phenomenologically by Angell, Ngai, Boehmer and others. The electronic materials discussed include a-Si:H, granular C 60 , semiconductor nanocrystallites, charge density waves in TaS 3 , spin glasses, and vortex glasses in high-temperature semiconductors. The molecular materials discussed include polymers, network glasses, electrolytes and alcohols, Van der Waals supercooled liquids and glasses, orientational glasses, water, fused salts, and heme proteins. In the intrinsic cases the theory of β(T g ) is often accurate to 2%, which

Some speculations on the critical exponents and fractal dimensionalities relevant to realistic spin glass alloys

International Nuclear Information System (INIS)

Mookerjee, A.

1984-09-01

The problem of spin-glass to ferromagnetic transition with increasing concentration is then one of the familiar nearest neighbour percolation but on the background of IIC. In the regime p<=psub(c) at T=Tsub(g)(p), the IIC forms a fractal background on which ferromagnetic percolation takes place. The equivalent statement is that the mobility edge Jsub(c)(p) moves outwards as p increases and at a critical psub(c) coincides with the band edge Jsub(B). At and above these concentrations the mode with highest energy is extended and we have the familiar paramagnetic to ferromagnetic transition as temperature is lowered across Jsub(B)/ksub(B). The physical justification of this picture is not at all transparent as in the case of the cluster percolation ideas. To this date no reliable estimates of the behaviour of Jsub(c)(p) as a function of p, for a purely off diagonal random matrix J(R) have been made

Class II glass ionomer/silver cermet restorations and their effect on interproximal growth of mutans streptococci.

Science.gov (United States)

Berg, J H; Farrell, J E; Brown, L R

1990-02-01

The release of fluoride from glass ionomer materials is one of the most important features of this newly implemented material, and the remineralization effects of this phenomenon have been documented (Hicks and Silverstone 1986). This paper examines the effects of glass ionomer/silver cermet restorations on the plaque levels of interproximal mutans streptococci. Fifteen patients with Class II lesions in primary molars were selected for study. Interproximal plaque samples were obtained from each of the lesion sites and from one caries-free site approximal to a primary molar. One lesion was restored with composite resin to serve as a treated control to the glass ionomer/silver cermet (Ketac Silver, ESPE/Premier Sales Corp., Norristown, Pennsylvania) test site. A sound (unaltered) interproximal site served as the untreated control site. Plaque samples were collected before and at one week, one month, and three months post-treatment. Samples were serially diluted to enable colony counts of mutans streptococci. One week post-treatment counts showed that the glass ionomer/silver cermet restorations significantly reduced (P less than 0.05) the approximal plaque levels of mutans streptococci. Conversely, the untreated and treated control sites did not exhibit reductions in approximal plaque levels of mutans streptococci. These results indicate that glass ionomer restorations may be inhibitory to the growth of mutans streptococci in dental plaque approximal to this restorative material in the primary dentition.

Structural investigations of some metallic glasses

International Nuclear Information System (INIS)

Sietsma, J.

1987-03-01

Metallic glasses were prepared by the melt spinning technique from iron and nickel alloys (Fe-Ni-P; Fe-B; Ni-Nb; Ni-B). Structure investigations were made by means of neutron diffraction experiments. Distribution functions and range orders were determined. (Auth.)

Evidence of spin-glass like ordering and exchange bias effect in antisite-disordered nanometric La{sub 1.5}Ca{sub 0.5}CoMnO{sub 6} double perovskite

Energy Technology Data Exchange (ETDEWEB)

Sahoo, R.C.; Paladhi, D.; Nath, T.K., E-mail: tnath@phy.iitkgp.ernet.in

2017-08-15

Highlights: • SG has been observed due to antisite disorder and different magnetic interactions. • The observed EB can be best explained on the basis of uncompensated interface spins. • −30% MR has been observed due to the spin-polarized transport at grain boundaries. - Abstract: Single-phase polycrystalline La{sub 1.5}Ca{sub 0.5}CoMnO{sub 6} 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 La{sub 1.5}Ca{sub 0.5}CoMnO{sub 6} (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 Co{sup 2+} and Mn{sup 4+} 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.

A new parallel algorithm for simulation of spin glasses on scales of space-time periods of external fields with consideration of relaxation effects

International Nuclear Information System (INIS)

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

2011-01-01

We have investigated the statistical properties of an ensemble of disordered 1D spatial spin chains (SSCs) of finite length, placed in an external field, with consideration of relaxation effects. The short-range interaction complex-classical Hamiltonian was first used for solving this problem. A system of recurrent equations is obtained on the nodes of the spin-chain lattice. An efficient mathematical algorithm is developed on the basis of these equations with consideration of the advanced Sylvester conditions which allow step by step construct a huge number of stable spin chains in parallel. The distribution functions of different parameters of spin-glass system are constructed from the first principles of the complex classical mechanics by analyzing the calculation results of the 1D SSCs ensemble. It is shown that the behavior of the parameter distributions is quite different depending on the external fields. The energy ensembles and constants of spin-spin interactions are changed smoothly depending on the external field in the limit of statistical equilibrium, while some of them such as the mean value of polarizations of ensemble and parameters of its orderings are frustrated. We have also studied some critical properties of the ensemble of such catastrophes in the Clausius-Mossotti equation depending on the value of the external field. We have shown that the generalized complex-classical approach excludes these catastrophes allowing one to organize continuous parallel computing on the whole region of values of the external field including critical points. A new representation of the partition function based on these investigations is suggested. As opposed to usual definition, this function is a complex one and its derivatives are everywhere defined, including critical points

Patch planting of hard spin-glass problems: Getting ready for the next generation of optimization approaches

Science.gov (United States)

Wang, Wenlong; Mandrà, Salvatore; Katzgraber, Helmut

We propose a patch planting heuristic that allows us to create arbitrarily-large Ising spin-glass instances on any topology and with any type of disorder, and where the exact ground-state energy of the problem is known by construction. By breaking up the problem into patches that can be treated either with exact or heuristic solvers, we can reconstruct the optimum of the original, considerably larger, problem. The scaling of the computational complexity of these instances with various patch numbers and sizes is investigated and compared with random instances using population annealing Monte Carlo and quantum annealing on the D-Wave 2X quantum annealer. The method can be useful for benchmarking of novel computing technologies and algorithms. NSF-DMR-1208046 and the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA), via MIT Lincoln Laboratory Air Force Contract No. FA8721-05-C-0002.

Spin-resolved x-ray photoemission studies of ferromagnetic metals

International Nuclear Information System (INIS)

Klebanoff, L.E.

1996-01-01

Recent spin-resolved x-ray photoelectron spectroscopy (SRXPS) studies of ferromagnetic metals are reviewed. SRXPS studies of metallic Fe, Co, Co 66 Fe 4 Ni 1 B 14 Si 15 , and Ni demonstrate that core-level photoemission, and the itinerant electron response to core-hole creation, are highly spin-dependent. The exchange splitting of the Fe 2p 3/2 level is found to be 0.48±0.05 eV. Lifetime broadening results for the Fe 2p 3/2 N↑ (majority spin) and N↓ (minority spin) components indicate conservation of spin in core-hole filling processes involving the valence band. SRXPS study of the Fe 2p 3/2 peak asymmetry α reveals a dependence of electron endash hole excitation on the spin of the core hole. Spin analysis of the Fe 3s XPS line shape shows it to be a three-component spectrum, rather than the two-component line shape assumed previously. A photon energy dependence of one of the Fe 3s components explains disagreement among previous Fe 3s XPS results. Comparisons of SRXPS from Co metal and Co 66 Fe 4 Ni 1 B 14 Si 15 directly demonstrate the effect of a reduced atomic magnetic moment on the spin dependence of core-level XPS. The behavior of lifetime broadenings for the N↑ and N↓ Co 2p 3/2 components show that the reduced Co magnetic moment found in the Co 66 Fe 4 Ni 1 B 14 Si 15 amorphous glass is due to the transfer of ↑-spin valence electron density to the ↓-spin valence band upon glass formation. SRXPS also allows investigation of spin-dependent core-hole screening processes and satellite production, as demonstrated in SRXPS studies of ferromagnetic Ni. Future directions of SRXPS are also explored. copyright 1996 American Vacuum Society

Nuclear spin dominated relaxation of atomic tunneling systems in glasses

Energy Technology Data Exchange (ETDEWEB)

Luck, Annina

2016-11-16

The measurements performed in this thesis have revealed a non phononic relaxation channel for atomic tunneling systems in glasses at very low temperatures due to the presence of nuclear electric quadrupoles. Dielectric measurements on the multicomponent glasses N-KZFS11 and HY-1, containing {sup 181}Ta and {sup 165}Ho, respectively, that both carry very large nuclear electric quadrupole moments, show a relaxation rate in the kilohertz range, that is constant for temperatures exceeding the nuclear quadrupole splitting of the relevant isotopes. The results are compared to measurements performed on the glasses Herasil and N-BK7 that both contain no large nuclear quadrupole moments. Using three different setups to measure the complex dielectric function, the measurements cover almost eight orders of magnitude in frequency from 60 Hz to 1 GHz and temperatures down to 7.5 mK. This has allowed us a detailed study of the novel effects observed within this thesis and has led to a simplified model explaining the effects of nuclear electric quadrupoles on the behavior of glasses at low temperatures. Numeric calculations based on this model are compared to the measured data.

Characterisation of spin-waves in copper(II) deuteroformate tetradeuterate: A square ¤S¤=1/2 Heisenberg antiferromagnet

DEFF Research Database (Denmark)

Clarke, S.J.; Harrison, A.; Mason, T.E.

1999-01-01

Copper(II) formate tetrahydrate (CFTH) is a model square S = 1/2 Heisenberg antiferromagnet with T-N = 16.54 +/- 0.05 K. The dispersion of spin-waves in the magnetic layers of a fully deuterated sample of this material has been mapped at 4.3 K by inelastic neutron scattering from the zone centre ...

Superparamagnetism and spin-glass like state for the MnFe{sub 2}O{sub 4} nano-particles synthesized by the thermal decomposition method

Energy Technology Data Exchange (ETDEWEB)

Gao Ruorui [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Zhang Yue, E-mail: yue-zhang@mail.hust.edu.cn [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Department of Electric Science and Technology, Huazhong University of Science and Technology, Wuhan 430074 (China); Yu Wei [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Xiong Rui [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Key Laboratory for the Green Preparation and Application of Functional Materials of Ministry of Education, Hubei University, Wuhan 430062 (China); Shi Jing [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Key Laboratory for the Green Preparation and Application of Functional Materials of Ministry of Education, Hubei University, Wuhan 430062 (China); International Center for Material Physics, Shen Yang 110015 (China)

2012-08-15

MnFe{sub 2}O{sub 4} nano-particles with an average size of about 7 nm were synthesized by the thermal decomposition method. Based on the magnetic hysteresis loops measured at different temperatures the temperature-dependent saturation magnetization (M{sub S}) and coercivity (H{sub C}) are determined. It is shown that above 20 K the temperature-dependence of the M{sub S} and H{sub C} indicates the magnetic behaviors in the single-domain nano-particles, while below 20 K, the change of the M{sub S} and H{sub C} indicates the freezing of the spin-glass like state on the surfaces. By measuring the magnetization-temperature (M-T) curves under the zero-field-cooling (ZFC) and field-cooling procedures at different applied fields, superparamagnetism behavior is also studied. Even though in the ZFC M-T curves peaks can be observed below 160 K, superparamagnetism does not appear until the temperature goes above 300 K, which is related with the strong inter-particle interaction. - Highlights: Black-Right-Pointing-Pointer MnFe{sub 2}O{sub 4} nano-particles with size of 7 nm were prepared. Black-Right-Pointing-Pointer The surface spin-glass like state is frozen below 20 K. Black-Right-Pointing-Pointer The peaks in ZFC magnetization-temperature curves are observed below 160 K. Black-Right-Pointing-Pointer The inter-particle interaction inhibits the superparamagnetism at room temperature.

Spin-exchange and spin-destruction rates for the 3He-Na system

International Nuclear Information System (INIS)

Borel, P.I.; Soegaard, L.V.; Svendsen, W.E.; Andersen, N.

2003-01-01

Optically pumped Na is used as a spin-exchange partner to polarize 3 He. Polarizations around 20% have routinely been achieved in sealed spherical glass cells containing 3 He, N 2 , and a few droplets of Na. An optical technique has been developed to determine the Na- 3 He spin-exchange rate coefficient. By monitoring the Na spin relaxation ''in the dark,'' the average Na-Na spin-destruction cross section at 330 degree sign C is estimated to be around 5x10 -19 cm 2 . This value is 2-5 (15-30) times smaller than the previously reported values for the K-K (Rb-Rb) spin-relaxation cross section. In the temperature range 310-355 degree sign C the spin-exchange rate coefficient is found to be (6.1±0.6)x10 -20 cm 3 /s with no detectable temperature dependence. This value is in good agreement with a previous theoretical estimate reported by Walker and it is only slightly lower than the corresponding Rb- 3 He spin-exchange rate coefficient. The total Na- 3 He spin-destruction rate coefficient is, within errors, found to be the same as the Na- 3 He spin-exchange rate coefficient, thereby indicating that the maximum possible photon efficiency may approach unity for the Na- 3 He system. A technique, in which a charge-coupled device camera is used to take images of faint unquenched fluorescence light, has been utilized to allow for an instantaneous determination of the sodium number densities during the rate coefficient measurements

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

International Nuclear Information System (INIS)

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

2015-01-01

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 (d l ) 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. (paper)

PREFACE: ELC International Meeting on Inference, Computation, and Spin Glasses (ICSG2013)

Science.gov (United States)

Kabashima, Yoshiyuki; Hukushima, Koji; Inoue, Jun-ichi; Tanaka, Toshiyuki; Watanabe, Osamu

2013-12-01

The close relationship between probability-based inference and statistical mechanics of disordered systems has been noted for some time. This relationship has provided researchers with a theoretical foundation in various fields of information processing for analytical performance evaluation and construction of efficient algorithms based on message-passing or Monte Carlo sampling schemes. The ELC International Meeting on 'Inference, Computation, and Spin Glasses (ICSG2013)', was held in Sapporo 28-30 July 2013. The meeting was organized as a satellite meeting of STATPHYS25 in order to offer a forum where concerned researchers can assemble and exchange information on the latest results and newly established methodologies, and discuss future directions of the interdisciplinary studies between statistical mechanics and information sciences. Financial support from Grant-in-Aid for Scientific Research on Innovative Areas, MEXT, Japan 'Exploring the Limits of Computation (ELC)' is gratefully acknowledged. We are pleased to publish 23 papers contributed by invited speakers of ICSG2013 in this volume of Journal of Physics: Conference Series. We hope that this volume will promote further development of this highly vigorous interdisciplinary field between statistical mechanics and information/computer science. Editors and ICSG2013 Organizing Committee: Koji Hukushima Jun-ichi Inoue (Local Chair of ICSG2013) Yoshiyuki Kabashima (Editor-in-Chief) Toshiyuki Tanaka Osamu Watanabe (General Chair of ICSG2013)

Crystallization behaviors and seal application of basalt based glass-ceramics

Science.gov (United States)

Ateş, A.; Önen, U.; Ercenk, E.; Yılmaz, Ş.

2017-02-01

Basalt based glass-ceramics were prepared by conventional melt-quenching technique and subsequently converted to glass-ceramics by a controlled nucleation and crystallization process. Glass materials were obtained by melt at 1500°C and quenched in cold water. The powder materials were made by milling and spin coating. The powders were applied on the 430 stainless steel interconnector material, and heat treatment was carried out. The interface characteristics between the glass-ceramic layer and interconnector were investigated by using X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The results showed that the basalt base glass-ceramic sealant material exhibited promising properties to use for SOFC.

Guest Induced Strong Cooperative One- and Two-Step Spin Transitions in Highly Porous Iron(II) Hofmann-Type Metal-Organic Frameworks.

Science.gov (United States)

Piñeiro-López, Lucı A; Valverde-Muñoz, Francisco Javier; Seredyuk, Maksym; Muñoz, M Carmen; Haukka, Matti; Real, José Antonio

2017-06-19

The synthesis, crystal structure, magnetic, calorimetric, and Mössbauer studies of a series of new Hofmann-type spin crossover (SCO) metal-organic frameworks (MOFs) is reported. The new SCO-MOFs arise from self-assembly of Fe II , bis(4-pyridyl)butadiyne (bpb), and [Ag(CN) 2 ] - or [M II (CN) 4 ] 2- (M II = Ni, Pd). Interpenetration of four identical 3D networks with α-Po topology are obtained for {Fe(bpb)[Ag I (CN) 2 ] 2 } due to the length of the rod-like bismonodentate bpb and [Ag(CN) 2 ] - ligands. The four networks are tightly packed and organized in two subsets orthogonally interpenetrated, while the networks in each subset display parallel interpenetration. This nonporous material undergoes a very incomplete SCO, which is rationalized from its intricate structure. In contrast, the single network Hofmann-type MOFs {Fe(bpb)[M II (CN) 4 ]}·nGuest (M II = Ni, Pd) feature enhanced porosity and display complete one-step or two-step cooperative SCO behaviors when the pores are filled with two molecules of nitrobenzene or naphthalene that interact strongly with the pyridyl and cyano moieties of the bpb ligands via π-π stacking. The lack of these guest molecules favors stabilization of the high-spin state in the whole range of temperatures. However, application of hydrostatic pressure induces one- and two-step SCO.

Kovacs effect in solvable model glasses

International Nuclear Information System (INIS)

Aquino, Gerardo; Leuzzi, Luca; Nieuwenhuizen, Theo M

2006-01-01

The Kovacs protocol, based on the temperature shift experiment originally conceived by A.J. Kovacs and applied on glassy polymers, is implemented in an exactly solvable model with facilitated dynamics. This model is based on interacting fast and slow modes represented respectively by spherical spins and harmonic oscillator variables. Due to this fundamental property and to slow dynamics, the model reproduces the characteristic nonmonotonic evolution known as the 'Kovacs effect', observed in polymers, spin glasses, in granular materials and models of molecular liquids, when similar experimental protocols are implemented

Kovacs effect in solvable model glasses

Science.gov (United States)

Aquino, Gerardo; Leuzzi, Luca; Nieuwenhuizen, Theo M.

2006-05-01

The Kovacs protocol, based on the temperature shift experiment originally conceived by A.J. Kovacs and applied on glassy polymers [1], is implemented in an exactly solvable model with facilitated dynamics. This model is based on interacting fast and slow modes represented respectively by spherical spins and harmonic oscillator variables. Due to this fundamental property and to slow dynamics, the model reproduces the characteristic nonmonotonic evolution known as the ''Kovacs effect'', observed in polymers, spin glasses, in granular materials and models of molecular liquids, when similar experimental protocols are implemented.

Ligand field and intermolecular interactions tuning the magnetic properties of spin-crossover Fe(II) polymer with 4,4′-bipyridine

Energy Technology Data Exchange (ETDEWEB)

Luo, Yang-Hui; Liu, Qing-Ling; Yang, Li-Jing; Ling, Yang; Wang, Wei; Sun, Bai-Wang, E-mail: chmsunbw@seu.edu.cn

2015-02-15

A new spin crossover coordination polymer (SCO-CPs) of Fe(II)-4,4′-bipyridine (4,4′-bipy) family: (Fe(4,4′-bipy){sub 2}(H{sub 2}O){sub 2})·(4,4′-bipy)· 8(H{sub 2}O)·2(ClO{sub 4}) (3), which displays half spin transitions between 100 and 300 K, has been synthesized and structurally characterized. Compound 3 featured with two-dimensional (2-D) grids connected by hydrogen bonds and π…π packing between one-dimensional (1-D) chains, the 2-D grids expand to three-dimensional (3-D) architecture supported by a “S-shaped holder” involving lattice 4-4′-bipy, water molecules and perchlorate anion. We compared 3 with the other two analogous complexes: ((Fe(4,4′-bipy) (H{sub 2}O){sub 2} (NCS){sub 2})·4,4′-bipy, 1 and (Fe(4,4′-bipy){sub 2}(NCS){sub 2})·mSolv, 2) through Hirshfeld surfaces analysis, which revealed that the low ligand field strength (NCS{sup −}) and lone-pair…H contacts contribute to the stabilization of HS (high-spin) state of the Fe(II) ion, while the high ligand field strength (4,4′-bipy) and strong intermolecular contacts (hydrogen bonds and π…π packing interactions) make for the LS (low-spin) state. - Highlights: ●A new member of Fe(||)-4,4′-bipy family has been prepared. ●It displays half spin transitions tuned by ligand field and intermolecular interactions. ●We have made a detailed comparison of this new member with two other analogous complexes.

Atomistic spin dynamics simulations on Mn-doped GaAs and CuMn

Energy Technology Data Exchange (ETDEWEB)

Hellsvik, Johan, E-mail: johan.hellsvik@fysik.uu.s [Department of Physics and Materials Science, Uppsala University, Box 530, SE-751 21 Uppsala (Sweden)

2010-01-01

The magnetic dynamical behavior of two random alloys have been investigated in atomistic spin dynamics (ASD) simulations. For both materials, magnetic exchange parameters calculated with first principles electronic structure methods were used. From experiments it is well known that CuMn is a highly frustrated magnetic system and a good manifestation of a Heisenberg spin glass. In our ASD simulations the behavior of the autocorrelation function indicate spin glass behavior. The diluted magnetic semiconductor (DMS) Mn-doped GaAs is engineered with hopes of high enough Curie temperatures to operate in spintronic devices. Impurities such as As antisites and Mn interstitials change the exhange couplings from being mainly ferromagnetic to also have antiferromagnetic components. We explore how the resulting frustration affects the magnetization dynamics for a varying rate of As antisites.

Real-time functional integral approach to the quantum disordered spin systems

International Nuclear Information System (INIS)

Kopec, T.K.

1989-01-01

In this paper the effect of randomness and frustration in the quantum Ising spin glass in a transverse field is studied by using the thermofield dynamics (TFD), the real time, finite temperature quantum field theory. It is shown that the method can be conveniently used for the averaging of the free energy of the system by completely avoiding the use of the n-replica trick. The effective dynamic Lagrangian for the disorder averaged causal, correlations and response Green functions is derived by functional integral approach. Furthermore, the properties of this Lagrangian are analyzed by the saddle point method which leads to the self-consistent equation for the spin glass order parameter

Properties and performance of spin-on-glass coatings for the corrosion protection of stainless steels in chloride media

DEFF Research Database (Denmark)

Lampert, Felix; Jensen, Annemette H.; Din, Rameez U.

2018-01-01

Spin-on-glass deposition was investigated as viable alternative to increase the durability and performance of 316L steel in chloride environment. The buildup of a detrimental interface oxide was prevented by non-oxidative thermal curing of the coatings, which leads to a transformation...... silica. Electrochemical analysis by cyclic polarization indicated that the coatings behave as imperfect barrier coatings, which may enhance the passive properties of the substrates; however, there is still some statistical scatter in the quality of the coatings. While there is a tendency for an increase...... of the upper limit of the breakdown potential, there is also a decrease of the lower limit. It was found that such lower quality coatings showed, in association with substrate defects, unevenly distributed coating flaws, which may act as initiation points of pitting corrosion and decrease the corrosion...

Glasses Containing Iron (II, III) Oxides For Immobilization Of Radioactive Technetium

International Nuclear Information System (INIS)

Kruger, A.A.; Heo, J.; Xu, K.; Choi, J.K.; Hrma, P.R.; Um, W.

2011-01-01

Technetium-99 (Tc-99) has posed serious environmental threats as US Department of Energy's high-level waste. This work reports the vitrification of Re, as surrogate for Tc-99, by iron-borosilicate and iron-phosphate glasses, respectively. Iron-phosphate glasses can dissolve Re as high as ∼ 1.2 wt. %, which can become candidate waste forms for Tc-99 disposal, while borosilicate glasses can retain less than 0.1 wt. % of Re due to high melting temperature and long melting duration. Vitrification of Re as Tc-99's mimic was investigated using iron-borosilicate and iron-phosphate glasses. The retention of Re in borosilicate glasses was less than 0.1 wt. % and more than 99 wt. % of Re were volatilized due to high melting temperature and long melting duration. Because the retention of Re in iron-phosphate glasses is as high as 1.2 wt. % and the volatilization is reduced down to ∼50 wt. %, iron-phosphate glasses can be one of the glass waste form candidates for Tc (or Re) disposal. The investigations of chemical durability and leaching test of iron-phosphate glasses containing Re are now underway to test the performance of the waste form.

Wavelength-selective bleaching of the optical spectra of trapped electrons in organic glasses. II

International Nuclear Information System (INIS)

Paraszczak, J.; Willard, J.E.

1979-01-01

Further resolution of the inhomogeneous optical spectra of trapped electrons (e - /sub t/) in organic glasses has been obtained from wavelength selective bleaching and thermal decay studies on 3-methylpentane-d 14 (3MP-d 14 ) and 2-methyltetrahydrofuran (MTHF) following γ irradiation in the temperature region of 20 K, and limits on the degree of resolution achievable have been indicated. Exposure of 3MP-d 14 to light of wavelengths >2100 nm (from a tunable laser) reduces the optical densities at the bleaching wavelength and longer to zero, while ''peeling off'' a portion of the O.D. at all shorter wavelengths but leaving the remainder of the spectrum unaffected. The fraction of the integrated optical spectrum, ∫OD d (eV), removed by bleaching at each wavelength tested, and also by thermal decay, is equivalent to the fraction of the total e - /sub t/ spins removed and measured by ESR. 1064 nm light bleaches the spectrum nearly uniformly, confirming that the spectra of all of the e - /sub t/ have blue tails with similar ease of bleaching. Heretofore unobserved low temperature thermal decay of e - /sub t/ occurs at 20 and 40 K (20% of the spin concentration in 30 min, 35% in 3h). The rate of decay of the optical spectrum decreases with decreasing wavelength of observation (2.5, 2.2, 1.8, and 1.5 μ), but at each wavelength is the same at 40 K as at 20 K, consistent

Nonanuclear Spin-Crossover Complex Containing Iron(II) and Iron(III) Based on a 2,6-Bis(pyrazol-1-yl)pyridine Ligand Functionalized with a Carboxylate Group.

Science.gov (United States)

Abhervé, Alexandre; Recio-Carretero, María José; López-Jordà, Maurici; Clemente-Juan, Juan Modesto; Canet-Ferrer, Josep; Cantarero, Andrés; Clemente-León, Miguel; Coronado, Eugenio

2016-09-19

The synthesis and magnetostructural characterization of [Fe(III)3(μ3-O)(H2O)3[Fe(II)(bppCOOH)(bppCOO)]6](ClO4)13·(CH3)2CO)6·(solvate) (2) are reported. This compound is obtained as a secondary product during synthesis of the mononuclear complex [Fe(II)(bppCOOH)2](ClO4)2 (1). The single-crystal X-ray diffraction structure of 2 shows that it contains the nonanuclear cluster of the formula [Fe(III)3(μ3-O)(H2O)3[Fe(II)(bppCOOH)(bppCOO)]6](13+), which is formed by a central Fe(III)3O core coordinated to six partially deprotonated [Fe(II)(bppCOOH)(bppCOO)](+) complexes. Raman spectroscopy studies on single crystals of 1 and 2 have been performed to elucidate the spin and oxidation states of iron in 2. These studies and magnetic characterization indicate that most of the iron(II) complexes of 2 remain in the low-spin (LS) state and present a gradual and incomplete spin crossover above 300 K. On the other hand, the Fe(III) trimer shows the expected antiferromagnetic behavior. From the structural point of view, 2 represents the first example in which bppCOO(-) acts as a bridging ligand, thus forming a polynuclear magnetic complex.

Search for the non-canonical Ising spin glass on rewired square lattices

Science.gov (United States)

Surungan, Tasrief

2018-03-01

A spin glass (SG) of non-canonical type is a purely antiferromagnetic (AF) system, exemplified by the AF Ising model on a scale free network (SFN), studied by Bartolozzi et al. [ Phys. Rev. B73, 224419 (2006)]. Frustration in this new type of SG is rendered by topological factor and its randomness is caused by random connectivity. As an SFN corresponds to a large dimensional lattice, finding non-canonical SG in lattice with physical dimension is desireable. However, a regular lattice can not have random connectivity. In order to obtain lattices with random connection and preserving the notion of finite dimension, we costructed rewired lattices. We added some extra bonds randomly connecting each site of a regular lattice to its next-nearest neighbors. Very recently, Surungan et al., studied AF Heisenberg system on rewired square lattice and found no SG behavior [AIP Conf. Proc. 1719, 030006 (2016)]. Due to the importance of discrete symmetry for phase transition, here we study similar structure for the Ising model (Z 2 symmetry). We used Monte Carlo simulation with Replica Exchange algorithm. Two types of structures were studied, firstly, the rewired square lattices with one extra bonds added to each site, and secondly, two bonds added to each site. We calculated the Edwards-Anderson paremeter, the commonly used parameter in searching for SG phase. The non-canonical SG is clearly observed in the rewired square lattice with two extra bonds added.

Stretched exponential relaxation in molecular and electronic glasses

Science.gov (United States)

Phillips, J. C.

1996-09-01

Stretched exponential relaxation, 0034-4885/59/9/003/img1, fits many relaxation processes in disordered and quenched electronic and molecular systems, but it is widely believed that this function has no microscopic basis, especially in the case of molecular relaxation. For electronic relaxation the appearance of the stretched exponential is often described in the context of dispersive transport, where 0034-4885/59/9/003/img2 is treated as an adjustable parameter, but in almost all cases it is generally assumed that no microscopic meaning can be assigned to 0034-4885/59/9/003/img3 even at 0034-4885/59/9/003/img4, a glass transition temperature. We show that for molecular relaxation 0034-4885/59/9/003/img5 can be understood, providing that one separates extrinsic and intrinsic effects, and that the intrinsic effects are dominated by two magic numbers, 0034-4885/59/9/003/img6 for short-range forces, and 0034-4885/59/9/003/img7 for long-range Coulomb forces, as originally observed by Kohlrausch for the decay of residual charge on a Leyden jar. Our mathematical model treats relaxation kinetics using the Lifshitz - Kac - Luttinger diffusion to traps depletion model in a configuration space of effective dimensionality, the latter being determined using axiomatic set theory and Phillips - Thorpe constraint theory. The experiments discussed include ns neutron scattering experiments, particularly those based on neutron spin echoes which measure S( Q,t) directly, and the traditional linear response measurements which span the range from 0034-4885/59/9/003/img8 to s, as collected and analysed phenomenologically by Angell, Ngai, Böhmer and others. The electronic materials discussed include a-Si:H, granular 0034-4885/59/9/003/img9, semiconductor nanocrystallites, charge density waves in 0034-4885/59/9/003/img10, spin glasses, and vortex glasses in high-temperature semiconductors. The molecular materials discussed include polymers, network glasses, electrolytes and alcohols, Van

Experimental evidence for simultaneous relaxation processes in super spin glass γ-Fe2O3 nanoparticle system

Science.gov (United States)

Nikolic, V.; Perovic, M.; Kusigerski, V.; Boskovic, M.; Mrakovic, A.; Blanusa, J.; Spasojevic, V.

2015-03-01

Spherical γ-Fe2O3 nanoparticles with the narrow size distribution of (5 ± 1) nm were synthesized by the method of thermal decomposition from iron acetyl acetonate precursor. The existence of super spin-glass state at low temperatures and in low applied magnetic fields was confirmed by DC magnetization measurements on a SQUID magnetometer. The comprehensive investigation of magnetic relaxation dynamics in low-temperature region was conducted through the measurements of single-stop and multiple stop ZFC memory effects, ZFC magnetization relaxation, and AC susceptibility measurements. The experimental findings revealed the peculiar change of magnetic relaxation dynamics at T ≈ 10 K, which arose as a consequence of simultaneous existence of different relaxation processes in Fe2O3 nanoparticle system. Complementarity of the applied measurements was utilized in order to single out distinct relaxation processes as well as to elucidate complex relaxation mechanisms in the investigated interacting nanoparticle system.

Is there a role for oligosaccharides in seed longevity? An assessment of intracellular glass stability

NARCIS (Netherlands)

Buitink, J.; Hemminga, M.A.; Hoekstra, F.A.

2000-01-01

We examined whether oligosaccharides extend seed longevity by increasing the intracellular glass stability. For that purpose, we used a spin probe technique to measure the molecular mobility and glass transition temperature of the cytoplasm of impatiens (Impatiens walleriana) and bell pepper

Optical pumping production of spin polarized hydrogen

International Nuclear Information System (INIS)

Knize, R.J.; Happer, W.; Cecchi, J.L.

1984-01-01

There has been much interest recently in the production of large quantities of spin polarized hydrogen in various fields including controlled fusion, quantum fluids, high energy, and nuclear physics. One promising method for the development of large quantities of spin polarized hydrogen is the utilization of optical pumping with a laser. Optical pumping is a process where photon angular momentum is converted into electron and nuclear spin. The advent of tunable CW dye lasers (approx. 1 watt) allow the production of greater than 10 18 polarized atoms/sec. We have begun a program at Princeton to investigate the physics and technology of using optical pumping to produce large quantities of spin polarized hydrogen. Initial experiments have been done in small closed glass cells. Eventually, a flowing system, open target, or polarized ion source could be constructed

Long-time predictability in disordered spin systems following a deep quench.

Science.gov (United States)

Ye, J; Gheissari, R; Machta, J; Newman, C M; Stein, D L

2017-04-01

We study the problem of predictability, or "nature vs nurture," in several disordered Ising spin systems evolving at zero temperature from a random initial state: How much does the final state depend on the information contained in the initial state, and how much depends on the detailed history of the system? Our numerical studies of the "dynamical order parameter" in Edwards-Anderson Ising spin glasses and random ferromagnets indicate that the influence of the initial state decays as dimension increases. Similarly, this same order parameter for the Sherrington-Kirkpatrick infinite-range spin glass indicates that this information decays as the number of spins increases. Based on these results, we conjecture that the influence of the initial state on the final state decays to zero in finite-dimensional random-bond spin systems as dimension goes to infinity, regardless of the presence of frustration. We also study the rate at which spins "freeze out" to a final state as a function of dimensionality and number of spins; here the results indicate that the number of "active" spins at long times increases with dimension (for short-range systems) or number of spins (for infinite-range systems). We provide theoretical arguments to support these conjectures, and also study analytically several mean-field models: the random energy model, the uniform Curie-Weiss ferromagnet, and the disordered Curie-Weiss ferromagnet. We find that for these models, the information contained in the initial state does not decay in the thermodynamic limit-in fact, it fully determines the final state. Unlike in short-range models, the presence of frustration in mean-field models dramatically alters the dynamical behavior with respect to the issue of predictability.

Long-time predictability in disordered spin systems following a deep quench

Science.gov (United States)

Ye, J.; Gheissari, R.; Machta, J.; Newman, C. M.; Stein, D. L.

2017-04-01

We study the problem of predictability, or "nature vs nurture," in several disordered Ising spin systems evolving at zero temperature from a random initial state: How much does the final state depend on the information contained in the initial state, and how much depends on the detailed history of the system? Our numerical studies of the "dynamical order parameter" in Edwards-Anderson Ising spin glasses and random ferromagnets indicate that the influence of the initial state decays as dimension increases. Similarly, this same order parameter for the Sherrington-Kirkpatrick infinite-range spin glass indicates that this information decays as the number of spins increases. Based on these results, we conjecture that the influence of the initial state on the final state decays to zero in finite-dimensional random-bond spin systems as dimension goes to infinity, regardless of the presence of frustration. We also study the rate at which spins "freeze out" to a final state as a function of dimensionality and number of spins; here the results indicate that the number of "active" spins at long times increases with dimension (for short-range systems) or number of spins (for infinite-range systems). We provide theoretical arguments to support these conjectures, and also study analytically several mean-field models: the random energy model, the uniform Curie-Weiss ferromagnet, and the disordered Curie-Weiss ferromagnet. We find that for these models, the information contained in the initial state does not decay in the thermodynamic limit—in fact, it fully determines the final state. Unlike in short-range models, the presence of frustration in mean-field models dramatically alters the dynamical behavior with respect to the issue of predictability.

71Ga-77Se connectivities and proximities in gallium selenide crystal and glass probed by solid-state NMR

Science.gov (United States)

Nagashima, Hiroki; Trébosc, Julien; Calvez, Laurent; Pourpoint, Frédérique; Mear, François; Lafon, Olivier; Amoureux, Jean-Paul

2017-09-01

We introduce two-dimensional (2D) 71Ga-77Se through-bond and through-space correlation experiments. Such correlations are achieved using (i) the J-mediated Refocused Insensitive Nuclei Enhanced by Polarization Transfer (J-RINEPT) method with 71Ga excitation and 77Se Carr-Purcell-Meiboon-Gill (CPMG) detection, as well as (ii) the J- or dipolar-mediated Hetero-nuclear Multiple-Quantum Correlation (J- or D-HMQC) schemes with 71Ga excitation and quadrupolar CPMG (QCPMG) detection. These methods are applied to the crystalline β-Ga2Se3 and the 0.2Ga2Se3-0.8GeSe2 glass. Such glass leads to a homogeneous and reproducible glass-ceramic, which is a good alternative to single-crystalline Ge and polycrystalline ZnSe materials for making lenses transparent in the IR range for thermal imaging applications. We show that 2D 71Ga-77Se correlation experiments allow resolving the 77Se signals of molecular units, which are not resolved in the 1D 77Se CPMG spectrum. Additionally, the build-up curves of the J-RINEPT and the J-HMQC experiments allow the estimate of the 71Ga-77Se J-couplings via one and three-bonds in the three-dimensional network of β-Ga2Se3. Furthermore, these build-up curves show that the one-bond 1J71Ga-77Se couplings in the 0.2Ga2Se3-0.8GeSe2 glass are similar to those measured for β-Ga2Se3. We also report 2D 71Ga Satellite Transition Magic-Angle Spinning (STMAS) spectrum of β-Ga2Se3 using QCPMG detection at high magnetic field and high Magic-Angle Spinning frequency using large radio frequency field. Such spectrum allows separating the signal of β-Ga2Se3 and that of an impurity.

Asymmetric electroresistance of cluster glass state in manganites

KAUST Repository

Lourembam, James; Ding, Junfeng; Bera, Ashok; Lin, Weinan; Wu, Tao

2014-01-01

cluster glass magnetic state emerges at low temperatures with a spin freezing temperature of about 99 K, which is accompanied by the reentrant insulating state with high resistance below 30 K. In the EDLT, we observe bipolar and asymmetric modulation

Ground-state magnetization of the Ising spin glass: A recursive numerical method and Chen-Ma scaling

Science.gov (United States)

Sepehrinia, Reza; Chalangari, Fartash

2018-03-01

The ground-state properties of quasi-one-dimensional (Q1D) Ising spin glass are investigated using an exact numerical approach and analytical arguments. A set of coupled recursive equations for the ground-state energy are introduced and solved numerically. For various types of coupling distribution, we obtain accurate results for magnetization, particularly in the presence of a weak external magnetic field. We show that in the weak magnetic field limit, similar to the 1D model, magnetization exhibits a singular power-law behavior with divergent susceptibility. Remarkably, the spectrum of magnetic exponents is markedly different from that of the 1D system even in the case of two coupled chains. The magnetic exponent makes a crossover from being dependent on a distribution function to a constant value independent of distribution. We provide an analytic theory for these observations by extending the Chen-Ma argument to the Q1D case. We derive an analytical formula for the exponent which is in perfect agreement with the numerical results.

Multi-layered metal nanocrystals in a sol-gel spin-on-glass matrix for flash memory applications

Energy Technology Data Exchange (ETDEWEB)

Huang, Meiyu Stella [Department of Chemical and Biomolecular Engineering, National University of Singapore, Block E5, 4 Engineering Drive 4, 117576 (Singapore); Globalfoundries Singapore Pte Ltd, 60 Woodlands Industrial Park D, 738406 (Singapore); Suresh, Vignesh [Department of Chemical and Biomolecular Engineering, National University of Singapore, Block E5, 4 Engineering Drive 4, 117576 (Singapore); Agency for Science, Technology and Research - A*Star, Institute of Materials Research and Engineering (IMRE), #08-03, 2 Fusionopolis Way, Innovis, 138634 (Singapore); Chan, Mei Yin [School of Materials Science and Engineering (MSE), Nanyang Technological University (NTU), 50 Nanyang Avenue, 639798 (Singapore); Ma, Yu Wei [Globalfoundries Singapore Pte Ltd, 60 Woodlands Industrial Park D, 738406 (Singapore); Lee, Pooi See [School of Materials Science and Engineering (MSE), Nanyang Technological University (NTU), 50 Nanyang Avenue, 639798 (Singapore); Krishnamoorthy, Sivashankar [Agency for Science, Technology and Research - A*Star, Institute of Materials Research and Engineering (IMRE), #08-03, 2 Fusionopolis Way, Innovis, 138634 (Singapore); Science et Analyse des Materiaux Unit (SAM), Centre de Recherche Public-Gabriel Lippmann, 41, rue du Brill, Belvaux, 4422 (Luxembourg); Srinivasan, M.P., E-mail: srinivasan.madapusi@rmit.edu.au [Department of Chemical and Biomolecular Engineering, National University of Singapore, Block E5, 4 Engineering Drive 4, 117576 (Singapore); School of Engineering, RMIT University, Building 10, Level 11, Room 14, 376-392 Swanston Street, Melbourne, Victoria, 3001 (Australia)

2017-01-15

A simple and low-cost process of embedding metal nanocrystals as charge storage centers within a dielectric is demonstrated to address leakage issues associated with the scaling of the tunnelling oxide in flash memories. Metal nanocrystals with high work functions (nickel, platinum and palladium) were prepared as embedded species in methyl siloxane spin-on-glass (SOG) films on silicon substrates. Sub-10 nm-sized, well-isolated, uniformly distributed, multi-layered nanocrystals with high particle densities (10{sup 11}–10{sup 12} cm{sup −2}) were formed in the films by thermal curing of the spin-coated SOG films containing the metal precursors. Capacitance-Voltage measurements performed on metal-insulator-semiconductor capacitors with the SOG films show that the presence of metal nanocrystals enhanced the memory window of the films to 2.32 V at low operating voltages of ±5 V. These SOG films demonstrated the ability to store both holes and electrons. Capacitance-time measurements show good charge retention of more than 75% after 10{sup 4} s of discharging. This work demonstrates the applicability of the low-cost in-situ sol-gel preparation in contrast to conventional methods that involve multiple and expensive processing steps. - Highlights: • Sub-10 nm sized, well-isolated, uniformly distributed nanoparticle based charge trap memories. • Preparation of multi-layer high work function metal nanocrystals at low cost. • Large memory window of 2.32 V at low operating voltages of ±5 V. • Good charge retention of more than 90% and 75% after 10{sup 3} and 10{sup 4} s of discharging respectively. • Use of a 3 nm thick tunnelling oxide in compliance with ITRS specifications.

Multi-layered metal nanocrystals in a sol-gel spin-on-glass matrix for flash memory applications

International Nuclear Information System (INIS)

Huang, Meiyu Stella; Suresh, Vignesh; Chan, Mei Yin; Ma, Yu Wei; Lee, Pooi See; Krishnamoorthy, Sivashankar; Srinivasan, M.P.

2017-01-01

A simple and low-cost process of embedding metal nanocrystals as charge storage centers within a dielectric is demonstrated to address leakage issues associated with the scaling of the tunnelling oxide in flash memories. Metal nanocrystals with high work functions (nickel, platinum and palladium) were prepared as embedded species in methyl siloxane spin-on-glass (SOG) films on silicon substrates. Sub-10 nm-sized, well-isolated, uniformly distributed, multi-layered nanocrystals with high particle densities (10"1"1–10"1"2 cm"−"2) were formed in the films by thermal curing of the spin-coated SOG films containing the metal precursors. Capacitance-Voltage measurements performed on metal-insulator-semiconductor capacitors with the SOG films show that the presence of metal nanocrystals enhanced the memory window of the films to 2.32 V at low operating voltages of ±5 V. These SOG films demonstrated the ability to store both holes and electrons. Capacitance-time measurements show good charge retention of more than 75% after 10"4 s of discharging. This work demonstrates the applicability of the low-cost in-situ sol-gel preparation in contrast to conventional methods that involve multiple and expensive processing steps. - Highlights: • Sub-10 nm sized, well-isolated, uniformly distributed nanoparticle based charge trap memories. • Preparation of multi-layer high work function metal nanocrystals at low cost. • Large memory window of 2.32 V at low operating voltages of ±5 V. • Good charge retention of more than 90% and 75% after 10"3 and 10"4 s of discharging respectively. • Use of a 3 nm thick tunnelling oxide in compliance with ITRS specifications.

Evidence of refilled chamber gas pressure enhancing cooling rate during melt spinning of a Zr50Cu40Al10 alloy

Directory of Open Access Journals (Sweden)

Hong-wang Yang

2015-07-01

Full Text Available The influence of the refilled gas pressure on the glass forming behaviour of one of the best ternary glass forming alloys Zr50Cu40Al10 was studied for the melt spinning process. The amorphicity of as-quenched ribbons was characterized by X-ray diffraction (XRD and differential scanning calorimetry (DSC. The refilled chamber atmospheric pressure is crucial to the cooling rate of melt spinning. At high vacuum, at pressure less than 0.0001 atm, fully crystalline fragments are obtained. Monolithic amorphous ribbons were only obtained at a gas pressure of 0.1 atm or higher. The extended contact length between thecribbons and the copper wheel contributes to the high cooling rate of melt spinning. Higher chamber gas pressure leads to more turbulence of liquid metal beneath the nozzle; therefore, lower pressure is preferable at practical melt spinning processes once glass forming conditions are fulfilled.

The light-induced spin transition of tetranuclear spin crossover complex [Fe4(CN)4(bpy)4(tpa)2](PF6)4

International Nuclear Information System (INIS)

Nishihara, T; Tanaka, K; Nihei, M; Oshio, H

2009-01-01

We report on the light induced spin transition in the tetranuclear spin crossover complex [Fe 4 (CN) 4 (bpy) 4 (tpa) 2 ](PF 6 ) 4 . The photo-conversion occurs at the specific site (Fe2) of four Fe II ions. The red light irradiation (1.79 eV) gives rise to full conversion of Fe2 into the high spin state from the low spin state. The green light irradiation (2.33 eV) can convert only the half of Fe2 into the high spin state, though the photo-conversion rate in the beginning is much higher than that with the red light. We present a simple model in which the photo-conversion kinetics is controlled by a large background absorption due to remaining three Fe II ions (Fe1, Fe3 and Fe4).

Quantum Glass of Interacting Bosons with Off-Diagonal Disorder

Science.gov (United States)

Piekarska, A. M.; Kopeć, T. K.

2018-04-01

We study disordered interacting bosons described by the Bose-Hubbard model with Gaussian-distributed random tunneling amplitudes. It is shown that the off-diagonal disorder induces a spin-glass-like ground state, characterized by randomly frozen quantum-mechanical U(1) phases of bosons. To access criticality, we employ the "n -replica trick," as in the spin-glass theory, and the Trotter-Suzuki method for decomposition of the statistical density operator, along with numerical calculations. The interplay between disorder, quantum, and thermal fluctuations leads to phase diagrams exhibiting a glassy state of bosons, which are studied as a function of model parameters. The considered system may be relevant for quantum simulators of optical-lattice bosons, where the randomness can be introduced in a controlled way. The latter is supported by a proposition of experimental realization of the system in question.

Predicting critical temperatures of iron(II) spin crossover materials: Density functional theory plus U approach

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yachao, E-mail: yczhang@nano.gznc.edu.cn [Guizhou Provincial Key Laboratory of Computational Nano-Material Science, Guizhou Normal College, Guiyang 550018, Guizhou (China)

2014-12-07

A first-principles study of critical temperatures (T{sub c}) of spin crossover (SCO) materials requires accurate description of the strongly correlated 3d electrons as well as much computational effort. This task is still a challenge for the widely used local density or generalized gradient approximations (LDA/GGA) and hybrid functionals. One remedy, termed density functional theory plus U (DFT+U) approach, introduces a Hubbard U term to deal with the localized electrons at marginal computational cost, while treats the delocalized electrons with LDA/GGA. Here, we employ the DFT+U approach to investigate the T{sub c} of a pair of iron(II) SCO molecular crystals (α and β phase), where identical constituent molecules are packed in different ways. We first calculate the adiabatic high spin-low spin energy splitting ΔE{sub HL} and molecular vibrational frequencies in both spin states, then obtain the temperature dependent enthalpy and entropy changes (ΔH and ΔS), and finally extract T{sub c} by exploiting the ΔH/T − T and ΔS − T relationships. The results are in agreement with experiment. Analysis of geometries and electronic structures shows that the local ligand field in the α phase is slightly weakened by the H-bondings involving the ligand atoms and the specific crystal packing style. We find that this effect is largely responsible for the difference in T{sub c} of the two phases. This study shows the applicability of the DFT+U approach for predicting T{sub c} of SCO materials, and provides a clear insight into the subtle influence of the crystal packing effects on SCO behavior.

On the stochastic dynamics of disordered spin models

International Nuclear Information System (INIS)

Semerjian, G.; Montanari, A.; Cugliandolo, L.F.

2003-09-01

In this article we discuss several aspects of the stochastic dynamics of spin models. The paper has two independent parts. Firstly, we explore a few properties of the multi-point correlations and responses of generic systems evolving in equilibrium with a thermal bath. We propose a fluctuation principle that allows us to derive fluctuation-dissipation relations for many-time correlations and linear responses. We also speculate on how these features will be modified in systems evolving slowly out of equilibrium, as finite-dimensional or dilute spin-glasses. Secondly, we present a formalism that allows one to derive a series of approximated equations that determine the dynamics of disordered spin models on random (hyper) graphs. (author)

Structure-topology-property correlations of sodium phosphosilicate glasses.

Science.gov (United States)

Hermansen, Christian; Guo, Xiaoju; Youngman, Randall E; Mauro, John C; Smedskjaer, Morten M; Yue, Yuanzheng

2015-08-14

In this work, we investigate the correlations among structure, topology, and properties in a series of sodium phosphosilicate glasses with [SiO2]/[SiO2 + P2O5] ranging from 0 to 1. The network structure is characterized by (29)Si and (31)P magic-angle spinning nuclear magnetic resonance and Raman spectroscopy. The results show the formation of six-fold coordinated silicon species in phosphorous-rich glasses. Based on the structural data, we propose a formation mechanism of the six-fold coordinated silicon, which is used to develop a quantitative structural model for predicting the speciation of the network forming units as a function of chemical composition. The structural model is then used to establish a temperature-dependent constraint description of phosphosilicate glass topology that enables prediction of glass transition temperature, liquid fragility, and indentation hardness. The topological constraint model provides insight into structural origin of the mixed network former effect in phosphosilicate glasses.

High-field spin dynamics of the one-dimensional spin-1/2 Heisenberg antiferromagnetα-bis (N-methylsalicylaldiminato copper) (II) (α-CuNSal)

International Nuclear Information System (INIS)

Azevedo, L.J.; Narath, A.; Richards, P.M.; Soos, Z.G.

1980-01-01

Proton spin-lattice relaxation rates in the one-dimensional (1D) spin-1/2 Heisenberg antiferromagnet α-bis (N-methylsalicylaldiminato) copper (II), α-CuNSal, have been measured in applied fields up to 125 kOe in the temperature range 1-- 4 K. The strong coupling of protons close to the antiferromagnetic (AF) chain serves as a convenient probe to study the dynamics of the AF chain through the field-induced antiferromagnetic to ferromagnetic (F) phase transition. The magnetization of the AF chain, as measured by the proton field shift, is in close agreement with calculations by Bonner and Fisher and yields an exchange interaction J/k/sub B/=3.04 +- 0.04 K. The proton relaxation rate has isotropic (hyperfine coupled) and anisotropic (dipolar) components. We identify the isotropic relaxation rate with a creation or destruction of one-spin excitations (magnons) and the anisotropic rate with two-magnon processes. The measured one-magnon relaxation rate shows an enhancement near the critical field for the AF → F transition and a strong decrease of more than four decades as the critical field is exceeded. A no-adjustable-parameter calculation based on the fermion model quantitatively agrees with the measured one-magnon relaxation rate, both above and below the critical field H/sub c/. The enhanced relaxation at H/sub c/ is correctly predicted as a consequence of the divergence of the 1D density of magnon states, where a gap in the spin-wave spectrum exists. Above H/sub c/ a finite magnon lifetime must be included in order to produce a nonzero one-magnon relaxation rate. This is also calculated with no adjustable parameters. The two-magnon relaxation rate also shows a decrease as the critical field is exceeded and the calculated relaxation rate agrees well with experiment at low temperatures, provided, however, that one uses a boson rather than fermion picture

Comparison of additive amount used in spin-coated and roll-coated organic solar cells

DEFF Research Database (Denmark)

Cheng, Pei; Lin, Yuze; Zawacka, Natalia Klaudia

2014-01-01

All-polymer and polymer/fullerene inverted solar cells were fabricated by spin-coating and roll-coating processes. The spin-coated small-area (0.04 cm(2)) devices were fabricated on indium tin oxide (ITO) coated glass substrates in nitrogen. The roll-coated large-area (1.0 cm(2)) devices were...

Heterogeneities in nuclear waste glass

International Nuclear Information System (INIS)

Ladirat, Ch.

1997-01-01

The industrial vitrification of high level radioactive wastes is a 2 stage process. During the first stage, the concentrated solution is heated in a spinning resistance oven at the temperature of 400 Celsius degrees till evaporation and calcination. The second stage begins when the dry residue falls into a melting pot that is maintained at a temperature of 1100-1150 Celsius degrees. Glass fretting is added and the glass is elaborated through the fusion of the different elements present in the melting pot. Heterogeneities in the glass may be associated to: - the presence in the solution to vitrify of insoluble elements from the dissolution of the fuel (RuO 2 , Rh, Pd), - the presence of minuscule metal scraps (Zr) that have been produced during the cutting of the fuel element, - the failures to conform to the technical specifications of the vitrification process, for instance, temperatures or flow rates when introducing the different elements in the melting pot. (A.C.)

High-level waste borosilicate glass: A compendium of corrosion characteristics. Volume 2

International Nuclear Information System (INIS)

Cunnane, J.C.

1994-03-01

The objective of this document is to summarize scientific information pertinent to evaluating the extent to which high-level waste borosilicate glass corrosion and the associated radionuclide release processes are understood for the range of environmental conditions to which waste glass may be exposed in service. Alteration processes occurring within the bulk of the glass (e.g., devitrification and radiation-induced changes) are discussed insofar as they affect glass corrosion.This document is organized into three volumes. Volumes I and II represent a tiered set of information intended for somewhat different audiences. Volume I is intended to provide an overview of waste glass corrosion, and Volume 11 is intended to provide additional experimental details on experimental factors that influence waste glass corrosion. Volume III contains a bibliography of glass corrosion studies, including studies that are not cited in Volumes I and II. Volume I is intended for managers, decision makers, and modelers, the combined set of Volumes I, II, and III is intended for scientists and engineers working in the field of high-level waste

High-level waste borosilicate glass: A compendium of corrosion characteristics. Volume 2

Energy Technology Data Exchange (ETDEWEB)

Cunnane, J.C. [comp.; Bates, J.K.; Bradley, C.R. [Argonne National Lab., IL (United States)] [and others

1994-03-01

The objective of this document is to summarize scientific information pertinent to evaluating the extent to which high-level waste borosilicate glass corrosion and the associated radionuclide release processes are understood for the range of environmental conditions to which waste glass may be exposed in service. Alteration processes occurring within the bulk of the glass (e.g., devitrification and radiation-induced changes) are discussed insofar as they affect glass corrosion.This document is organized into three volumes. Volumes I and II represent a tiered set of information intended for somewhat different audiences. Volume I is intended to provide an overview of waste glass corrosion, and Volume 11 is intended to provide additional experimental details on experimental factors that influence waste glass corrosion. Volume III contains a bibliography of glass corrosion studies, including studies that are not cited in Volumes I and II. Volume I is intended for managers, decision makers, and modelers, the combined set of Volumes I, II, and III is intended for scientists and engineers working in the field of high-level waste.

Overview of spin physics

International Nuclear Information System (INIS)

Yokosawa, A.

1992-01-01

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

Structure and properties of barium tin boro-phosphate glass systems with very low photoelastic constant

Science.gov (United States)

Itadani, M.; Tricot, G.; Doumert, B.; Takebe, H.; Saitoh, A.

2017-08-01

Glasses in the BaO-SnO-P2O5-B2O3 system were prepared and evaluated in order to formulate preform glasses suitable for the fabrication of fiber cores with a very low photoelastic constant. A first glass system (I: xBaO-(60-x)SnO-40P2O5) was designed with a constant P2O5 content and various BaO contents (0-40 mol. %). Introduction of 3 mol. % of B2O3 to enhance the glass stability leads to the second glass system (II: x'BaO-(57-x')SnO-40P2O5-3B2O3) with 33-38 mol. % BaO. The structure of both systems was investigated by 1D/2D magic-angle spinning nuclear magnetic resonance, Raman, and Fourier transform infrared spectroscopic techniques. 31P NMR showed the presence of Q2 and Q1 units in the first system and correlation 11B/31P NMR indicated that boron enters into the network as B(OP)4 structural units. The photoelastic constant was determined and the stability of the best formulations as well as their refractive index dispersion was established. The drawing temperature and isothermal heating time (without crystal precipitation) parameters were also accurately measured by using experimental time-temperature-transition. Considering that the refractive indices of the core and the cladding materials must match, detailed core and cladding compositions for a fiber enabling single-mode waveguide transmission were proposed.

Kovacs effect in a model for a fragile glass

Science.gov (United States)

Aquino, Gerardo; Leuzzi, Luca; Nieuwenhuizen, Theo M.

2006-03-01

The Kovacs protocol, based on the temperature shift experiment originally conceived by A. J. Kovacs for glassy polymers, is implemented in an exactly solvable dynamical model. This model is characterized by interacting fast and slow modes represented, respectively, by spherical spins and harmonic oscillator variables. Due to this fundamental property, the model reproduces the characteristic nonmonotonic evolution known as the “Kovacs effect,” observed in polymers, spin glasses, granular materials, and molecular liquid models, when similar experimental protocols are implemented.

Fe++/Fe+++ concentration relationship and mechanical properties of phosphate glasses useful for wastes immobilization

International Nuclear Information System (INIS)

Garcia, D.A.; Prado, Miguel O.

2007-01-01

Under different melting conditions, glasses with different Fe(II)/Fe(III) concentration relationship were prepared within each type of glass 43Fe 2 O 3 -57P 2 O 5 and 33,33Fe 2 O 3 - 66,67P 2 O 5 . Using Moessbauer spectroscopy Fe(II)/Fe(III) concentration values were determined. Vickers and Knoop indentations were used for determining their hardness, toughness, Young modulus and brittleness. The same measurements were carried on some silicate and aluminosilicate glasses. Also Weibull statistics was done to determine the characteristics (Weibull modulus and and fracture probability) of glass fracture. We found that silicate glasses (SG) are harder than phosphate glasses (PG). Toughness values for PG, are in the same range than for SG, although for the same density exhibit larger values or smaller brittleness than silicate glasses. For one of the glasses it was found that the mechanical load P 0 needed for a fracture probability of 63% increases with the Fe(II) content. (author)

Durability testing with West Valley borosilicate glass composition- Phase II

International Nuclear Information System (INIS)

Macedo, P.B.; Finger, S.M.; Barkatt, A.A.; Pegg, I.L.; Feng, X.; Freeborn, W.P.

1988-06-01

This report presents the research performed by the Catholic University of America Vitreous State Laboratory (VSL) during FY 1987 in support of the West Valley Demonstration Project (WVDP) nuclear waste vitrification process. A principal objective of this work is the optimization of the glass composition be used for the vitrification of the liquid high-level waste generated at West Valley during nuclear fuel reprocessing. This report discusses (1) the experimental investigations to optimize the reference glass composition (the current leading candidates are WVCM-50 and ATM-10) for the WVDP vitrification process; (2) the systematic experimental investigation performed to determine the effects of compositional variations in WVCM-50 and WV-205 reference glasses on their viscosity and durability (including initial results of long-term leach tests of WVCM-50 under repository conditions); (3) the development of short-time and predictive leach tests; (4) the development of a process model for the West Valley vitrification process which predicts the range of glass compositions which may be encountered during normal operations and the effects of deviations in process control parameters; and (5) the development of product models for predicting the durability and viscosity of nuclear waste glasses

Spin waves in terbium. II. Magnon-phonon interaction

International Nuclear Information System (INIS)

Jensen, J.; Houmann, J.G.

1975-01-01

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

Moessbauer spectroscopy studies of spin reorientations in amorphous and crystalline (Co0.2Fe0.8)72.5Si12.5B15 glass coated micro-wires

International Nuclear Information System (INIS)

Nowik, I.; Felner, I.; Garcia-Miquel, H.

2007-01-01

Thermo-gravimetric, differential scanning calorimetry and comprehensive 57 Fe Moessbauer spectroscopy studies of amorphous and crystalline ferromagnetic glass coated (Co 0.2 Fe 0.8 ) 72.5 Si 12.5 B 15 micro-wires have been recorded. The Curie temperature of the amorphous phase is T C (amorp) ∼730 K. The analysis of the Moessbauer spectra reveals that below 623 K the easy axis of the magnetization is axial-along the wires, and that a tangential or/and radial orientation occurs at higher temperatures. At 770 K, in the first 4 hours the Moessbauer spectrum exhibits a pure paramagnetic doublet. Crystallization and decomposition to predominantly α-Fe(Si) and Fe 2 B occurs either by raising the temperature above 835 K or isothermally in time at lower temperatures. Annealing for a day at 770 K, leads to crystallization. In the crystalline material the magnetic moments have a complete random orientation. After cooling back to ambient temperature, both α-Fe(Si) and Fe 2 B in the glass coated wire show pure axial magnetic orientation like in the original amorphous state. The observed spin reorientations are associated with changes in the stress induced by the glass coating

Memo, "Incorporation of HLW Glass Shell V2.0 into the Flowsheets," to ED Lee, CCN: 184905, October 20, 2009

Energy Technology Data Exchange (ETDEWEB)

Gimpel, Rodney F.; Kruger, Albert A.

2013-12-18

Efforts are being made to increase the efficiency and decrease the cost of vitrifying radioactive waste stored in tanks at the U.S. Department of Energy Hanford Site. The compositions of acceptable and processable high-level waste (HL W) glasses need to be optimized to minimize the waste-form volume and, hence, to reduce cost. A database of glass properties of waste glass and associated simulated waste glasses was collected and documented in PNNL 18501, Glass Property Data and Models for Estimating High-Level Waste Glass Volume and glass property models were curve-fitted to the glass compositions. A routine was developed that estimates HL W glass volumes using the following glass property models: II Nepheline, II One-Percent Crystal Temperature (T1%), II Viscosity (11) II Product Consistency Tests (PCT) for boron, sodium, and lithium, and II Liquidus Temperature (TL). The routine, commonly called the HL W Glass Shell, is presented in this document. In addition to the use of the glass property models, glass composition constraints and rules, as recommend in PNNL 18501 and in other documents (as referenced in this report) were incorporated. This new version of the HL W Glass Shell should generally estimate higher waste loading in the HL W glass than previous versions.

Biocorrosion Evaluation on a Zr-Cu-Ag-Ti Metallic Glass

Science.gov (United States)

Kumar, Shresh; Anwar, Rebin; Ryu, Wookha; Park, E. S.; Vincent, S.

2018-04-01

Metallic glasses are in high demand for fabrication of variety of innovative products, in particular surgical and biomedical tools and devices owing to its excellent biocompatible properties. In the present investigation, a novel Zr39.5Cu50.5Ag4Ti6 metallic glass composition was synthesized using melt spinning technique. Potentiodynamic polarization studies were conducted to investigate bio-corrosion behaviour of Zr39.5Cu50.5Ag4Ti6 metallic glass. The test were conducted in various simulated artificial body conditions such as artificial saliva solution, phosphate-buffered saline solution, artificial blood plasma solution, and Hank’s balanced saline solution. The bio-corrosion results of metallic glass were compared with traditional biomaterials. The study aims to provide bio-compatible properties of Zr39.5Cu50.5Ag4Ti6 metallic glass.

Coexistence of ferromagnetism and unconventional spin-glass freezing in the site-disordered kagome ferrite SrS n2F e4O11

Science.gov (United States)

Shlyk, L.; Strobel, S.; Farmer, B.; De Long, L. E.; Niewa, R.

2018-02-01

Single-crystal x-ray diffraction refinements indicate SrS n2F e4O11 crystallizes in the hexagonal R -type ferrite structure with noncentrosymmetric space group P 63m c and lattice parameters a =5.9541 (2 )Å , c =13.5761 (5 )Å , Z =2 (R (F )=0.034 ). Octahedrally coordinated 2 a [M (1) and M (1a)] and 6 c sites [M (2 )] have random, mixed occupation by Sn and Fe; whereas the tetrahedrally coordinated 2 b sites [Fe(3) and Fe(3a)] are exclusively occupied by Fe, whose displacement from the ideal position with trigonal-bipyramidal coordination causes the loss of inversion symmetry. Our dc and ac magnetization data indicate SrS n2F e4O11 single crystals undergo a ferro- or ferri-magnetic transition below a temperature TC=630 K with very low coercive fields μoHc ⊥=0.27 Oe and μoHc ∥=1.5 Oe at 300 K, for applied field perpendicular and parallel to the c axis, respectively. The value for TC is exceptionally high, and the coercive fields exceptionally low, among the known R-type ferrites. Time-dependent dc magnetization and frequency-dependent ac magnetization data indicate the onset of short-range, spin-glass freezing below Tf=35.8 K , which results from crystallographic disorder of magnetic F e3 + and nonmagnetic S n4 + ions on a frustrated Kagome sublattice. Anomalous ac susceptibility and thermomagnetic relaxation behavior in the short-range-ordered state differs from that of conventional spin glasses. Optical measurements in the ultraviolet to visible frequency range in a diffuse reflectance geometry indicate an overall optical band gap of 0.8 eV, consistent with observed semiconducting properties.

Manganese(II), iron(II), and mixed-metal metal-organic frameworks based on chains with mixed carboxylate and azide bridges: magnetic coupling and slow relaxation.

Science.gov (United States)

Wang, Yan-Qin; Yue, Qi; Qi, Yan; Wang, Kun; Sun, Qian; Gao, En-Qing

2013-04-15

Mn(II) and Fe(II) compounds derived from azide and the zwitterionic 1-carboxylatomethylpyridinium-4-carboxylate ligand are isomorphous three-dimensional metal-organic frameworks (MOFs) with the sra net, in which the metal ions are connected into anionic chains by mixed (μ-1,1-azide)bis(μ-carboxylate) triple bridges and the chains are cross-linked by the cationic backbones of the zwitterionic ligands. The Mn(II) MOFs display typical one-dimensional antiferromagnetic behavior. In contrast, with one more d electron per metal center, the Fe(II) counterpart shows intrachain ferromagnetic interactions and slow relaxation of magnetization attributable to the single-chain components. The activation energies for magnetization reversal in the infinite- and finite-chain regimes are Δτ1 = 154 K and Δτ2 = 124 K, respectively. Taking advantage of the isomorphism between the Mn(II) and Fe(II) MOFs, we have prepared a series of mixed-metal Mn(II)(1-x)Fe(II)(x) MOFs with x = 0.41, 0.63, and 0.76, which intrinsically feature random isotropic/anisotropic sites and competing antiferromagnetic-ferromagnetic interactions. The materials show a gradual antiferromagnetic-to-ferromagnetic evolution in overall behaviors as the Fe(II) content increases, and the Fe-rich materials show complex relaxation processes that may arise for mixed SCM and spin-glass mechanisms. A general trend is that the activation energy and the blocking temperature increase with the Fe(II) content, emphasizing the importance of anisotropy for slow relaxation of magnetization.

The influence of ligand field effects on the magnetic exchange of high-spin Co(II)-semiquinonate complexes.

Science.gov (United States)

Bencini, Alessandro; Beni, Alessandra; Costantino, Ferdinando; Dei, Andrea; Gatteschi, Dante; Sorace, Lorenzo

2006-02-07

[Co(Me(4)cyclam)(tropolonate)](PF(6)) was synthesised and structurally characterised. Its electronic and W-band EPR spectra have been analysed by means of the angular overlap calculation of the Spin Hamiltonian parameters that provided also a satisfactory reproduction of the temperature dependence of the magnetic susceptibility. The present results can be interpreted assuming a pseudo-octahedral character for the Co(II) center. This prompted us to reconsider the model formerly used for the analysis of the magnetic coupling between hs-Co(II) and the paramagnetic o-semiquinonate ligand in the corresponding derivatives [Co(Me(4)cyclam)(PhenSQ)](PF(6)) and [Co(Me(4)cyclam)(DTBSQ)](PF(6)). These results indicate that the effect of the magnetic coupling is active only below 50 K and that a more refined model of exchange coupling between Co(II) and semiquinonato ligands is needed to quantitatively analyze the magnetic behaviour of this class of systems.

And the World Turned: Spin Testing the DG-1000S

Science.gov (United States)

2015-10-01

mainly glass-fiber reinforced plastic, with steel as necessary for the landing gear. Load factor limits are +7/- 5g . Manufactured in Germany, the DG...Forward CG’s carry an additional type of risk for spin testing: structural failure due to over- speed /overload. After spin entry, if the aircraft’s...become “sloppy” in the DG-1000S near stall speed , careful attention to the yaw string was required for coordinated flight: anything less tended to cause

Magnetic resonance in spin glasses, superconductivity of thin aluminum films and models for transport properties of one dimensional systems

International Nuclear Information System (INIS)

Elliott, J.H.

1983-01-01

This thesis reports on three separate investigations in solid state physics. The first is electron paramagnetic resonance in the spin glass Ag:Mn. EPR measurements were performed at two resonance frequencies, concentrating on temperatures above the glass transition temperature. The measured linewidth appears to diverge at T/sub g/ for low resonance frequencies. These results will be compared with recently proposed phenomenological and microscopic theories. The second topic reported in this thesis is the superconducting transition of thin aluminum films. These films were investigated as a function of grain size and thickness. The transition temperature was enhanced over the bulk value, in agreement with many previous investigations of granular aluminum. The third topic reported in this thesis is an extension of the variable rate hopping theory applied in one dimension to N-ME-Qn(TCNQ) 2 . This model is a classical one used to explain both the dc and ac electrical conductivity of organic conductors. The temperature dependence of the model does not agree with experiment at low temperatures. Tunneling has been added to the hopping. This increases the conductivity at low temperatures, and results in excellent agreement with the experimental conductivity over the measured temperature range. The model also predicts that the frequency dependence of the conductivity varies as ω/sup .5/ at low frequencies. This long time tail prediction agrees with the measured dielectric constant of N-Me-iso-Qn(TCNQ) 2

The Role of Self-Interaction Corrections, Vibrations, and Spin-Orbit in Determining the Ground Spin State in a Simple Heme

Directory of Open Access Journals (Sweden)

Der-you Kao

2017-10-01

Full Text Available Without self-interaction corrections or the use of hybrid functionals, approximations to the density-functional theory (DFT often favor intermediate spin systems over high-spin systems. In this paper, we apply the recently proposed Fermi–Löwdin-orbital self-interaction corrected density functional formalism to a simple tetra-coordinated Fe(II-porphyrin molecule and show that the energetic orderings of the S = 1 and S = 2 spin states are changed qualitatively relative to the results of Generalized Gradient Approximation (developed by Perdew, Burke, and Ernzerhof, PBE-GGA and Local Density Approximation (developed by Perdew and Wang, PW92-LDA. Because the energetics, associated with changes in total spin, are small, we have also calculated the second-order spin–orbit energies and the zero-point vibrational energies to determine whether such corrections could be important in metal-substituted porphins. Our results find that the size of the spin–orbit and vibrational corrections to the energy orderings are small compared to the changes due to the self-interaction correction. Spin dependencies in the Infrared (IR/Raman spectra and the zero-field splittings are provided as a possible means for identifying the spin in porphyrins containing Fe(II.

Heating-induced glass-glass and glass-liquid transformations in computer simulations of water

Science.gov (United States)

Chiu, Janet; Starr, Francis W.; Giovambattista, Nicolas

2014-03-01

Water exists in at least two families of glassy states, broadly categorized as the low-density (LDA) and high-density amorphous ice (HDA). Remarkably, LDA and HDA can be reversibly interconverted via appropriate thermodynamic paths, such as isothermal compression and isobaric heating, exhibiting first-order-like phase transitions. We perform out-of-equilibrium molecular dynamics simulations of glassy water using the ST2 model to study the evolution of LDA and HDA upon isobaric heating. Depending on pressure, glass-to-glass, glass-to-crystal, glass-to-vapor, as well as glass-to-liquid transformations are found. Specifically, heating LDA results in the following transformations, with increasing heating pressures: (i) LDA-to-vapor (sublimation), (ii) LDA-to-liquid (glass transition), (iii) LDA-to-HDA-to-liquid, (iv) LDA-to-HDA-to-liquid-to-crystal, and (v) LDA-to-HDA-to-crystal. Similarly, heating HDA results in the following transformations, with decreasing heating pressures: (a) HDA-to-crystal, (b) HDA-to-liquid-to-crystal, (c) HDA-to-liquid (glass transition), (d) HDA-to-LDA-to-liquid, and (e) HDA-to-LDA-to-vapor. A more complex sequence may be possible using lower heating rates. For each of these transformations, we determine the corresponding transformation temperature as function of pressure, and provide a P-T "phase diagram" for glassy water based on isobaric heating. Our results for isobaric heating dovetail with the LDA-HDA transformations reported for ST2 glassy water based on isothermal compression/decompression processes [Chiu et al., J. Chem. Phys. 139, 184504 (2013)]. The resulting phase diagram is consistent with the liquid-liquid phase transition hypothesis. At the same time, the glass phase diagram is sensitive to sample preparation, such as heating or compression rates. Interestingly, at least for the rates explored, our results suggest that the LDA-to-liquid (HDA-to-liquid) and LDA-to-HDA (HDA-to-LDA) transformation lines on heating are related

Heating-induced glass-glass and glass-liquid transformations in computer simulations of water

International Nuclear Information System (INIS)

Chiu, Janet; Giovambattista, Nicolas; Starr, Francis W.

2014-01-01

Water exists in at least two families of glassy states, broadly categorized as the low-density (LDA) and high-density amorphous ice (HDA). Remarkably, LDA and HDA can be reversibly interconverted via appropriate thermodynamic paths, such as isothermal compression and isobaric heating, exhibiting first-order-like phase transitions. We perform out-of-equilibrium molecular dynamics simulations of glassy water using the ST2 model to study the evolution of LDA and HDA upon isobaric heating. Depending on pressure, glass-to-glass, glass-to-crystal, glass-to-vapor, as well as glass-to-liquid transformations are found. Specifically, heating LDA results in the following transformations, with increasing heating pressures: (i) LDA-to-vapor (sublimation), (ii) LDA-to-liquid (glass transition), (iii) LDA-to-HDA-to-liquid, (iv) LDA-to-HDA-to-liquid-to-crystal, and (v) LDA-to-HDA-to-crystal. Similarly, heating HDA results in the following transformations, with decreasing heating pressures: (a) HDA-to-crystal, (b) HDA-to-liquid-to-crystal, (c) HDA-to-liquid (glass transition), (d) HDA-to-LDA-to-liquid, and (e) HDA-to-LDA-to-vapor. A more complex sequence may be possible using lower heating rates. For each of these transformations, we determine the corresponding transformation temperature as function of pressure, and provide a P-T “phase diagram” for glassy water based on isobaric heating. Our results for isobaric heating dovetail with the LDA-HDA transformations reported for ST2 glassy water based on isothermal compression/decompression processes [Chiu et al., J. Chem. Phys. 139, 184504 (2013)]. The resulting phase diagram is consistent with the liquid-liquid phase transition hypothesis. At the same time, the glass phase diagram is sensitive to sample preparation, such as heating or compression rates. Interestingly, at least for the rates explored, our results suggest that the LDA-to-liquid (HDA-to-liquid) and LDA-to-HDA (HDA-to-LDA) transformation lines on heating are related

Heating-induced glass-glass and glass-liquid transformations in computer simulations of water

Energy Technology Data Exchange (ETDEWEB)

Chiu, Janet; Giovambattista, Nicolas [Department of Physics, Brooklyn College of the City University of New York, Brooklyn, New York 11210 (United States); Starr, Francis W. [Department of Physics, Wesleyan University, Middletown, Connecticut 06459 (United States)

2014-03-21

Water exists in at least two families of glassy states, broadly categorized as the low-density (LDA) and high-density amorphous ice (HDA). Remarkably, LDA and HDA can be reversibly interconverted via appropriate thermodynamic paths, such as isothermal compression and isobaric heating, exhibiting first-order-like phase transitions. We perform out-of-equilibrium molecular dynamics simulations of glassy water using the ST2 model to study the evolution of LDA and HDA upon isobaric heating. Depending on pressure, glass-to-glass, glass-to-crystal, glass-to-vapor, as well as glass-to-liquid transformations are found. Specifically, heating LDA results in the following transformations, with increasing heating pressures: (i) LDA-to-vapor (sublimation), (ii) LDA-to-liquid (glass transition), (iii) LDA-to-HDA-to-liquid, (iv) LDA-to-HDA-to-liquid-to-crystal, and (v) LDA-to-HDA-to-crystal. Similarly, heating HDA results in the following transformations, with decreasing heating pressures: (a) HDA-to-crystal, (b) HDA-to-liquid-to-crystal, (c) HDA-to-liquid (glass transition), (d) HDA-to-LDA-to-liquid, and (e) HDA-to-LDA-to-vapor. A more complex sequence may be possible using lower heating rates. For each of these transformations, we determine the corresponding transformation temperature as function of pressure, and provide a P-T “phase diagram” for glassy water based on isobaric heating. Our results for isobaric heating dovetail with the LDA-HDA transformations reported for ST2 glassy water based on isothermal compression/decompression processes [Chiu et al., J. Chem. Phys. 139, 184504 (2013)]. The resulting phase diagram is consistent with the liquid-liquid phase transition hypothesis. At the same time, the glass phase diagram is sensitive to sample preparation, such as heating or compression rates. Interestingly, at least for the rates explored, our results suggest that the LDA-to-liquid (HDA-to-liquid) and LDA-to-HDA (HDA-to-LDA) transformation lines on heating are related

Towards spin injection into silicon

Energy Technology Data Exchange (ETDEWEB)

Dash, S.P.

2007-08-15

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

Spin diffusion and torques in disordered antiferromagnets

KAUST Repository

Manchon, Aurelien

2017-02-01

We have developed a drift-diffusion equation of spin transport in collinear bipartite metallic antiferromagnets. Starting from a model tight-binding Hamiltonian, we obtain the quantum kinetic equation within Keldysh formalism and expand it to the lowest order in spatial gradient using Wigner expansion method. In the diffusive limit, these equations track the spatio-temporal evolution of the spin accumulations and spin currents on each sublattice of the antiferromagnet. We use these equations to address the nature of the spin transfer torque in (i) a spin-valve composed of a ferromagnet and an antiferromagnet, (ii) a metallic bilayer consisting of an antiferromagnet adjacent to a heavy metal possessing spin Hall effect, and in (iii) a single antiferromagnet possessing spin Hall effect. We show that the latter can experience a self-torque thanks to the non-vanishing spin Hall effect in the antiferromagnet.

Spin diffusion and torques in disordered antiferromagnets

KAUST Repository

Manchon, Aurelien

2017-01-01

We have developed a drift-diffusion equation of spin transport in collinear bipartite metallic antiferromagnets. Starting from a model tight-binding Hamiltonian, we obtain the quantum kinetic equation within Keldysh formalism and expand it to the lowest order in spatial gradient using Wigner expansion method. In the diffusive limit, these equations track the spatio-temporal evolution of the spin accumulations and spin currents on each sublattice of the antiferromagnet. We use these equations to address the nature of the spin transfer torque in (i) a spin-valve composed of a ferromagnet and an antiferromagnet, (ii) a metallic bilayer consisting of an antiferromagnet adjacent to a heavy metal possessing spin Hall effect, and in (iii) a single antiferromagnet possessing spin Hall effect. We show that the latter can experience a self-torque thanks to the non-vanishing spin Hall effect in the antiferromagnet.

Spacer type mediated tunable spin crossover (SCO) characteristics of pyrene decorated 2,6-bis(pyrazol-1-yl)pyridine (bpp) based Fe(ii) molecular spintronic modules.

Science.gov (United States)

Kumar, Kuppusamy Senthil; Šalitroš, Ivan; Moreno-Pineda, Eufemio; Ruben, Mario

2017-08-14

A simple "isomer-like" variation of the spacer group in a set of Fe(ii) spin crossover (SCO) complexes designed to probe spin state dependence of electrical conductivity in graphene-based molecular spintronic junctions led to the observation of remarkable variations in the thermal- and light-induced magnetic characteristics, paving a simple route for the design of functional SCO complexes with different temperature switching regimes based on a 2,6-bis(pyrazol-1-yl)pyridine ligand skeleton.

Experimental evidence for simultaneous relaxation processes in super spin glass γ-Fe{sub 2}O{sub 3} nanoparticle system

Energy Technology Data Exchange (ETDEWEB)

Nikolic, V.; Perovic, M., E-mail: mara.perovic@vinca.rs; Kusigerski, V.; Boskovic, M.; Mrakovic, A.; Blanusa, J.; Spasojevic, V. [University of Belgrade, Condensed Matter Physics Laboratory, Institute of Nuclear Sciences Vinca (Serbia)

2015-03-15

Spherical γ-Fe{sub 2}O{sub 3} nanoparticles with the narrow size distribution of (5 ± 1) nm were synthesized by the method of thermal decomposition from iron acetyl acetonate precursor. The existence of super spin-glass state at low temperatures and in low applied magnetic fields was confirmed by DC magnetization measurements on a SQUID magnetometer. The comprehensive investigation of magnetic relaxation dynamics in low-temperature region was conducted through the measurements of single-stop and multiple stop ZFC memory effects, ZFC magnetization relaxation, and AC susceptibility measurements. The experimental findings revealed the peculiar change of magnetic relaxation dynamics at T ≈ 10 K, which arose as a consequence of simultaneous existence of different relaxation processes in Fe{sub 2}O{sub 3} nanoparticle system. Complementarity of the applied measurements was utilized in order to single out distinct relaxation processes as well as to elucidate complex relaxation mechanisms in the investigated interacting nanoparticle system.

A review on organic spintronic materials and devices: II. Magnetoresistance in organic spin valves and spin organic light emitting diodes

Directory of Open Access Journals (Sweden)

Rugang Geng

2016-09-01

Full Text Available In the preceding review paper, Paper I [Journal of Science: Advanced Materials and Devices 1 (2016 128–140], we showed the major experimental and theoretical studies on the first organic spintronic subject, namely organic magnetoresistance (OMAR in organic light emitting diodes (OLEDs. The topic has recently been of renewed interest as a result of a demonstration of the magneto-conductance (MC that exceeds 1000% at room temperature using a certain type of organic compounds and device operating condition. In this report, we will review two additional organic spintronic devices, namely organic spin valves (OSVs where only spin polarized holes exist to cause magnetoresistance (MR, and spin organic light emitting diodes (spin-OLEDs where both spin polarized holes and electrons are injected into the organic emissive layer to form a magneto-electroluminescence (MEL hysteretic loop. First, we outline the major advances in OSV studies for understanding the underlying physics of the spin transport mechanism in organic semiconductors (OSCs and the spin injection/detection at the organic/ferromagnet interface (spinterface. We also highlight some of outstanding challenges in this promising research field. Second, the first successful demonstration of spin-OLEDs is reviewed. We also discuss challenges to achieve the high performance devices. Finally, we suggest an outlook on the future of organic spintronics by using organic single crystals and aligned polymers for the spin transport layer, and a self-assembled monolayer to achieve more controllability for the spinterface.

Low temperature spin dynamics and high pressure effects in frustrated pyrochlores

Science.gov (United States)

Mirebeau, Isabelle

2008-03-01

Frustrated pyrochlores R2M2O7, where R^3+ is a rare earth and M^4+ a transition or sp metal ion, show a large variety of exotic magnetic states due to the geometrical frustration of the pyrochlore lattice, consisting of corner sharing tetrahedra for both R and M ions. Neutron scattering allows one to measure their magnetic ground state as well as the spin fluctuations, in a microscopic way. An applied pressure may change the subtle energy balance between magnetic interactions, inducing new magnetic states. In this talk, I will review recent neutron results on Terbium pyrochlores, investigated by high pressure neutron diffraction and inelastic neutron scattering. Tb2M2O7 pyrochlores show respectively a spin liquid state for M=Ti [1], an ordered spin ice state for M= Sn [2], and a spin glass state with chemical order for M=Mo [3]. In Tb2Ti2O7 spin liquid, where only Tb^3+ ions are magnetic, an applied pressure induces long range antiferromagnetic order due to a small distortion of the lattice and magneto elastic coupling [4]. In Tb2Sn2O7, the substitution of Ti^4+ by the bigger Sn^4+ ion expands the lattice, inducing a long range ordered ferromagnetic state, with the local structure of a spin ice [2] and unconventional spin fluctuations [2,5]. The local ground state and excited crystal field states of the Tb^3+ ion were recently investigated by inelastic neutron scattering in both compounds [6]. Tb2Mo2O7, where Mo^4+ ions are also magnetic, shows an even more rich behaviour, due to the complex interaction between frustrated Tb and Mo lattices, having respectively localized and itinerant magnetism. In Tb2Mo2O7 spin glass, the lattice expansion induced by Tb/La substitution yields an ordered ferromagnetic state, which transforms back to spin glass under applied pressure [7]. New data about the spin fluctuations in these compounds, as measured by inelastic neutron scattering, will be presented. The talk will be dedicated to the memory of Igor Goncharenko, a renowned

A 2D rhomboidal system of manganese(ii) [Mn(3-MeC6H4COO)2(H2O)2]n with spin canting: rationalization of the magnetic exchange.

Science.gov (United States)

Garcia-Cirera, Beltzane; Costa, Ramon; Moreira, Ibério de P R; Font-Bardia, Mercè; Corbella, Montserrat

2018-03-12

The crystal structure of Mn(ii) carboxylate with 3-methylbenzoate as a bridging ligand [Mn(3-MeC 6 H 4 COO) 2 (H 2 O) 2 ] n shows a rhomboidal layer, where each pair of neighbor Mn(ii) ions are bridged through only one carboxylate group with a syn-anti conformation. The magnetic exchange between neighbor ions is weakly antiferromagnetic (J = -0.52 cm -1 , g = 2.04), and at low temperature the system shows spin canting with T B = 3.8 K. Computational studies, based on periodic calculations of the energies of the significant spin states on the magnetic cell and some higher supercells, corroborate the weak AF interaction between the adjacent Mn(ii) ions and preclude the negligible effect of frustration caused by very weak interactions between the non-adjacent ions in the magnetic response of the system. The results provide compelling evidence that the observed spin canting is due to the local coordination geometry of the manganese ions leading to two antiferromagnetically coupled subnets with different axial vectors.

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.

Influence of low-temperature annealing on magnetic properties of (Nd0.625Ni0.375)85Al15 metallic glass

International Nuclear Information System (INIS)

Xu Feng; Wang Zhiming; Chen Guang; Jiang Jianzhong; Du Youwei

2008-01-01

After a review of the selection process of (Nd 0.625 Ni 0.375 ) 85 Al 15 as a metallic glass with a relatively high glass-forming ability, we investigate the influences of its phase transitions by duplicating the heating process of the isochronal thermal analysis with low-temperature annealings. The structure, thermal stability and magnetic properties are characterized. And the influences on magnetic properties are particularly discussed with emphasis. Both the annealing processes, to the glass-transition temperature and to the onset temperature of crystallization, bring about a higher coercivity of the sample and a higher freezing temperature of the spin-glass-state. For the sample annealed to the onset temperature of crystallization, the influence is quite obvious and is ascribed to the formation of ferrimagnetic Nd 7 Ni 3 phase, as detected by XRD. For the sample annealed to the glass-transition temperature, the indistinct influence is further identified with the analysis of the frequency dependence of the spin-glass-state, and it is mainly attributed to the change of the short-range order in the amorphous matrix

The Spin Structure of the Neutron Determined Using a Polarized He-3 Target

Energy Technology Data Exchange (ETDEWEB)

Middleton, H

2004-01-06

Described is a study of the internal spin structure of the neutron performed by measuring the asymmetry in spin-dependent deep inelastic scattering of polarized electrons from nuclear polarized {sup 3}He. Stanford Linear Accelerator experiment E142's sample of 400 million scattering events collected at beam energies between 19 and 26 GeV led to the most precise measurement of a nucleon spin structure function to date. The {sup 3}He target represents a major advance in polarized target technology, using the technique of spin exchange with optically pumped rubidium vapor to produce a typical {sup 3}He nuclear polarization of 34% in a 30cm long target cell with a gas density of 2.3 x 10{sup 20} cm{sup -3}. The target polarization was measured to {+-}7% using an Adiabatic Fast Passage NMR system calibrated with the thermal equilibrium polarization of the protons in a sample of water. The relatively high polarization and target thickness were the result of the development of large volume glass target cells which had inherent nuclear spin relaxation times for the {sup 3}He gas of as long as 70 hours. A target cell production procedure is presented which focuses on special glass blowing techniques to minimize surface interactions with the {sup 3}He nuclei and careful gas purification and vacuum system procedures to reduce relaxation inducing impurities.

Glass-like and Verwey transitions in magnetite in details

Czech Academy of Sciences Publication Activity Database

Janů, Zdeněk; Hadač, J.; Švindrych, Z.

2007-01-01

Roč. 310, - (2007), e203-e205 ISSN 0304-8853 Institutional research plan: CEZ:AV0Z10100520 Keywords : metal-insulator transition s and other electronic transition s * spin glass es and other random magnets * dynamic properties Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.704, year: 2007

Energy landscapes in proteins and glasses

Science.gov (United States)

Singh, Sadanand

Soft materials are ubiquitous in our day-to-day life. They include liquids, colloids, polymers, foams, gels, granular systems, and a number of biological materials. While these materials exhibit a wide range of textures and morphologies, many of their properties have common physicochemical origins. A better understanding of such origins would lead to rational design and engineering of functional soft materials. A common feature of soft materials is the wide range of time and length scales that characterizes their behavior. Unfortunately, available molecular modeling techniques are often ill-suited for problems that exhibit multiple length and time scales. In this thesis, we introduce and implement new simulation methods that have enabled molecular-level studies of soft materials. Such methods permit calculation of free energy surfaces, and we demonstrate their usefulness in the context of proteins and glasses, both of which exhibit rugged free energy landscapes. A first application is concerned with human amylin, a protein associated with Type II diabetes. Patients with Type II diabetes exhibit fibrillar deposits of human amylin protein in the pancreas. By applying the advanced simulation methods and algorithms developed in this work, we investigate the structure and folding dynamics of human amylin. A detailed mechanism is presented at the atomic-level for the nucleation and aggregation of the peptide. The results presented in this work could help in development of therapeutic strategies for Type II diabetes. The second application is concerned with the study of vapor-deposited ultrastable glasses. These stable glasses have, far below the conventional glass transition temperature, the properties expected from the equilibrium supercooled liquid state. Our results indicate that optimal stability is attained when deposition occurs near the Kauzmann temperature. We also show that the extraordinary stability of model vapor deposited glasses is associated with distinct

Field control of anisotropic spin transport and spin helix dynamics in a modulation-doped GaAs quantum well

Science.gov (United States)

Anghel, S.; Passmann, F.; Singh, A.; Ruppert, C.; Poshakinskiy, A. V.; Tarasenko, S. A.; Moore, J. N.; Yusa, G.; Mano, T.; Noda, T.; Li, X.; Bristow, A. D.; Betz, M.

2018-03-01

Electron spin transport and dynamics are investigated in a single, high-mobility, modulation-doped, GaAs quantum well using ultrafast two-color Kerr-rotation microspectroscopy, supported by qualitative kinetic theory simulations of spin diffusion and transport. Evolution of the spins is governed by the Dresselhaus bulk and Rashba structural inversion asymmetries, which manifest as an effective magnetic field that can be extracted directly from the experimental coherent spin precession. A spin-precession length λSOI is defined as one complete precession in the effective magnetic field. It is observed that application of (i) an out-of-plane electric field changes the spin decay time and λSOI through the Rashba component of the spin-orbit coupling, (ii) an in-plane magnetic field allows for extraction of the Dresselhaus and Rashba parameters, and (iii) an in-plane electric field markedly modifies both the λSOI and diffusion coefficient.

Glass transition in thin supported polystyrene films probed by temperature-modulated ellipsometry in vacuum.

Science.gov (United States)

Efremov, Mikhail Yu; Kiyanova, Anna V; Last, Julie; Soofi, Shauheen S; Thode, Christopher; Nealey, Paul F

2012-08-01

Glass transition in thin (1-200 nm thick) spin-cast polystyrene films on silicon surfaces is probed by ellipsometry in a controlled vacuum environment. A temperature-modulated modification of the method is used alongside a traditional linear temperature scan. A clear glass transition is detected in films with thicknesses as low as 1-2 nm. The glass transition temperature (T(g)) shows no substantial dependence on thickness for coatings greater than 20 nm. Thinner films demonstrate moderate T(g) depression achieving 18 K for thicknesses 4-7 nm. Less than 4 nm thick samples are excluded from the T(g) comparison due to significant thickness nonuniformity (surface roughness). The transition in 10-20 nm thick films demonstrates excessive broadening. For some samples, the broadened transition is clearly resolved into two separate transitions. The thickness dependence of the glass transition can be well described by a simple 2-layer model. It is also shown that T(g) depression in 5 nm thick films is not sensitive to a wide range of experimental factors including molecular weight characteristics of the polymer, specifications of solvent used for spin casting, substrate composition, and pretreatment of the substrate surface.

Transparent nanocrystalline ZnO films prepared by spin coating

Energy Technology Data Exchange (ETDEWEB)

Berber, M. [SusTech GmbH and Co. KG, Petersenstr. 20, 64287 Darmstadt, Hessen (Germany)]. E-mail: mete.berber@sustech.de; Bulto, V. [SusTech GmbH and Co. KG, Petersenstr. 20, 64287 Darmstadt, Hessen (Germany); Kliss, R. [SusTech GmbH and Co. KG, Petersenstr. 20, 64287 Darmstadt, Hessen (Germany); Hahn, H. [SusTech GmbH and Co. KG, Petersenstr. 20, 64287 Darmstadt, Hessen (Germany); Forschungszentrum Karlsruhe, Institute for Nanotechnology, Postfach 3640, 76021 Karlsruhe (Germany); Joint Research Laboratory Nanomaterials, TU Darmstadt, Institute of Materials Science, Petersenstr. 23, 64287 Darmstadt (Germany)

2005-09-15

Dispersions of zinc oxide nanoparticles synthesized by the electrochemical deposition under oxidizing conditions process with organic surfactants, were spin coated on glass substrates. After sintering, the microstructure, surface morphology, and electro-optical properties of the transparent nanocrystalline zinc oxide films have been investigated for different coating thicknesses and organic solvents.

Transparent nanocrystalline ZnO films prepared by spin coating

International Nuclear Information System (INIS)

Berber, M.; Bulto, V.; Kliss, R.; Hahn, H.

2005-01-01

Dispersions of zinc oxide nanoparticles synthesized by the electrochemical deposition under oxidizing conditions process with organic surfactants, were spin coated on glass substrates. After sintering, the microstructure, surface morphology, and electro-optical properties of the transparent nanocrystalline zinc oxide films have been investigated for different coating thicknesses and organic solvents

Strength and Fractography of Glass Wool Fibres

DEFF Research Database (Denmark)

Lund, Majbritt Deichgræber; Yue, Yuanzheng

  Glass wool fibres (GWFs) are produced using the cascade spinning process. The lengths of the fibers range from 1 to 4 cm, whereas the diameters range from 4 and 10 mm. GWFs are widely used as insulation material due to their excellent heat and sound isolation effect, chemical durability, and high...... between fracture strength (sf) and mirror radius (r), i.e., sf = A*r, is confirmed for all the GWFs studied. The materials constant, A, (mirror constant) is found to be 2.4 ~ 2.7 MPam½ for basaltic wool and 2.0 MPam½ for E-glass wool, which is similar to the value reported in the literature for different...

Theory of glass

International Nuclear Information System (INIS)

Rivier, N.

1985-01-01

The physical properties of glass are direct consequences of its non-crystalline structure. The structure is described from a topological point of view, since topology is the only geometry surviving non-crystallinity, i.e. absence of metric and trivial space group. This fact has two main consequences: the overall homogeneity of glass is a gauge symmetry, and the only extended, structurally stable constituents are odd lines (or 2π-disclinations in the elastic continuum limit). A gauge theory of glass, based on odd lines as sources of frozen-in strain, can explain those properties of glasses which are both specific to, and universal in amorphous solids: low-temperature excitations, and relaxation at high temperatures. The methods of statistical mechanics can be applied to give a minimal description of amorphous structures in statistical equilibrium. Criteria for statistical equilibrium of the structure and detailed balance are given, together with structural equations of state, which turn out to be well-known empirically among botanists and metallurgists. This review is based on lectures given in 1984 in Niteroi. It contains five parts: I - Structure, from a topological viewpoint; II - gauge invariance; III - Tunneling modes; IV - Supercooled liquid and the glass transitions; V - Statistical crystallography. (Author) [pt

Q-Speciation and Network Structure Evolution in Invert Calcium Silicate Glasses.

Science.gov (United States)

Kaseman, Derrick C; Retsinas, A; Kalampounias, A G; Papatheodorou, G N; Sen, S

2015-07-02

Binary silicate glasses in the system CaO-SiO2 are synthesized over an extended composition range (42 mol % ≤ CaO ≤ 61 mol %), using container-less aerodynamic levitation techniques and CO2-laser heating. The compositional evolution of Q speciation in these glasses is quantified using (29)Si and (17)O magic angle spinning nuclear magnetic resonance spectroscopy. The results indicate progressive depolymerization of the silicate network upon addition of CaO and significant deviation of the Q speciation from the binary model. The equilibrium constants for the various Q species disproportionation reactions for these glasses are found to be similar to (much smaller than) those characteristic of Li (Mg)-silicate glasses, consistent with the corresponding trends in the field strengths of these modifier cations. Increasing CaO concentration results in an increase in the packing density and structural rigidity of these glasses and consequently in their glass transition temperature Tg. This apparent role reversal of conventional network-modifying cations in invert alkaline-earth silicate glasses are compared and contrasted with that in their alkali silicate counterparts.

Entanglement property in matrix product spin systems

International Nuclear Information System (INIS)

Zhu Jingmin

2012-01-01

We study the entanglement property in matrix product spin-ring systems systemically by von Neumann entropy. We find that: (i) the Hilbert space dimension of one spin determines the upper limit of the maximal value of the entanglement entropy of one spin, while for multiparticle entanglement entropy, the upper limit of the maximal value depends on the dimension of the representation matrices. Based on the theory, we can realize the maximum of the entanglement entropy of any spin block by choosing the appropriate control parameter values. (ii) When the entanglement entropy of one spin takes its maximal value, the entanglement entropy of an asymptotically large spin block, i.e. the renormalization group fixed point, is not likely to take its maximal value, and so only the entanglement entropy S n of a spin block that varies with size n can fully characterize the spin-ring entanglement feature. Finally, we give the entanglement dynamics, i.e. the Hamiltonian of the matrix product system. (author)

Tunnel restorations using glass ionomer or glass cermet: in vitro marginal ridge fracture and microleakage.

Science.gov (United States)

Shetty, R; Munshi, A K

1996-01-01

The purpose of this in vitro study was to compare the marginal ridge fracture resistance and microleakage following restorations of partial tunnel preparations using glass ionomer and glass cermet cements. Sixty eight sound premolars were selected for this study and were divided randomly into six groups. A standardized partial tunnel preparation was done on all the teeth except specimens belonging to Group I. The partial tunnel preparations of Groups III & V were restored with glass ionomer and that of Groups IV & VI were restored with glass cermet. The teeth belonging to Groups I, II, III & IV were subjected to marginal ridge fracture resistance testing. The teeth of Groups V & VI were tested for microleakage after immersing them in 5% methylene blue solution for 4 hours. The results indicated that the teeth restored with glass cermet were marginally better than that with glass ionomer in terms of marginal ridge fracture resistance. Both the materials failed to reinforce the marginal ridge to the level of an intact tooth. The microleakage which occurred around both the materials were statistically insignificant, but on comparison glass ionomer showed better results. Hence, glass ionomer is preferred as a restorative material for partial tunnel preparations because of additional inherent advantages like superior esthetics and fluoride leachability.

Temperature-induced structural changes in fluorozirconate glasses and liquids

International Nuclear Information System (INIS)

Sen, S.; Youngman, R.E.

2002-01-01

The atomic structure and its temperature dependence in fluorozirconate glasses and supercooled liquids have been studied with high-resolution and high-temperature 19 F and 23 Na nuclear-magnetic-resonance (NMR) spectroscopy. The 19 F NMR spectra in these glasses show the presence of multiple F environments. Temperature dependence of the 19 F magic-angle-spinning NMR spectra indicates a progressive change in the average F coordination environment in the glass structure, besides motional narrowing due to substantial mobility of F - ions. The observed change in the average 19 F NMR chemical shift is consistent with progressive breaking of the Zr-F-Zr linkages in the glass structure with increasing temperature. The onset of such a change in F speciation is observed at temperatures well below T g . This result is evidence of changes in the average equilibrium structure in an inorganic glass-forming liquid at T g , albeit on a local scale. The 23 Na NMR spectra indicate that the cations in these glasses become significantly mobile only at temperatures T≥T g , which allows for the onset of global structural relaxation and viscous flow

Atmospheric Processing of Volcanic Glass: Effects on Iron Solubility and Redox Speciation.

Science.gov (United States)

Maters, Elena C; Delmelle, Pierre; Bonneville, Steeve

2016-05-17

Volcanic ash from explosive eruptions can provide iron (Fe) to oceanic regions where this micronutrient limits primary production. Controls on the soluble Fe fraction in ash remain poorly understood but Fe solubility is likely influenced during atmospheric transport by condensation-evaporation cycles which induce large pH fluctuations. Using glass powder as surrogate for ash, we experimentally simulate its atmospheric processing via cycles of pH 2 and 5 exposure. Glass fractional Fe solubility (maximum 0.4%) is governed by the pH 2 exposure duration rather than by the pH fluctuations, however; pH 5 exposure induces precipitation of Fe-bearing nanoparticles which (re)dissolve at pH 2. Glass leaching/dissolution release Fe(II) and Fe(III) which are differentially affected by changes in pH; the average dissolved Fe(II)/Fetot ratio is ∼0.09 at pH 2 versus ∼0.18 at pH 5. Iron release at pH 2 from glass with a relatively high bulk Fe(II)/Fetot ratio (0.5), limited aqueous Fe(II) oxidation at pH 5, and possibly glass-mediated aqueous Fe(III) reduction may render atmospherically processed ash a significant source of Fe(II) for phytoplankton. By providing new insight into the form(s) of Fe associated with ash as wet aerosol versus cloud droplet, we improve knowledge of atmospheric controls on volcanogenic Fe delivery to the ocean.

Structural Iron (II) of Basaltic Glass as an Energy Source for Zetaproteobacteria in an Abyssal Plain Environment, Off the Mid Atlantic Ridge.

Science.gov (United States)

Henri, Pauline A; Rommevaux-Jestin, Céline; Lesongeur, Françoise; Mumford, Adam; Emerson, David; Godfroy, Anne; Ménez, Bénédicte

2015-01-01

To explore the capability of basaltic glass to support the growth of chemosynthetic microorganisms, complementary in situ and in vitro colonization experiments were performed. Microbial colonizers containing synthetic tholeitic basaltic glasses, either enriched in reduced or oxidized iron, were deployed off-axis from the Mid Atlantic Ridge on surface sediments of the abyssal plain (35°N; 29°W). In situ microbial colonization was assessed by sequencing of the 16S rRNA gene and basaltic glass alteration was characterized using Scanning Electron Microscopy, micro-X-ray Absorption Near Edge Structure at the Fe-K-edge and Raman microspectroscopy. The colonized surface of the reduced basaltic glass was covered by a rind of alteration made of iron-oxides trapped in a palagonite-like structure with thicknesses up to 150 μm. The relative abundance of the associated microbial community was dominated (39% of all reads) by a single operational taxonomic unit (OTU) that shared 92% identity with the iron-oxidizer Mariprofundus ferrooxydans PV-1. Conversely, the oxidized basaltic glass showed the absence of iron-oxides enriched surface deposits and correspondingly there was a lack of known iron-oxidizing bacteria in the inventoried diversity. In vitro, a similar reduced basaltic glass was incubated in artificial seawater with a pure culture of the iron-oxidizing M. ferrooxydans DIS-1 for 2 weeks, without any additional nutrients or minerals. Confocal Laser Scanning Microscopy revealed that the glass surface was covered by twisted stalks characteristic of this iron-oxidizing Zetaproteobacteria. This result supported findings of the in situ experiments indicating that the Fe(II) present in the basalt was the energy source for the growth of representatives of Zetaproteobacteria in both the abyssal plain and the in vitro experiment. In accordance, the surface alteration rind observed on the reduced basaltic glass incubated in situ could at least partly result from their activity.

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.

Iron phosphate glasses: Bulk properties and atomic scale structure

Energy Technology Data Exchange (ETDEWEB)

Joseph, Kitheri; Stennett, Martin C.; Hyatt, Neil C.; Asuvathraman, R.; Dube, Charu L.; Gandy, Amy S.; Govindan Kutty, K. V.; Jolley, Kenny; Vasudeva Rao, P. R.; Smith, Roger

2017-10-01

Bulk properties such as glass transition temperature, density and thermal expansion of iron phosphate glass compositions, with replacement of Cs by Ba, are investigated as a surrogate for the transmutation of 137Cs to 137Ba, relevant to the immobilisation of Cs in glass. These studies are required to establish the appropriate incorporation rate of 137Cs in iron phosphate glass. Density and glass transition temperature increases with the addition of BaO indicating the shrinkage and reticulation of the iron phosphate glass network. The average thermal expansion coefficient reduces from 19.8 × 10-6 K-1 to 13.4 × 10-6 K-1, when 25 wt. % of Cs2O was replaced by 25 wt. % of BaO in caesium loaded iron phosphate glass. In addition to the above bulk properties, the role of Ba as a network modifier in the structure of iron phosphate glass is examined using various spectroscopic techniques. The FeII content and average coordination number of iron in the glass network was estimated using Mössbauer spectroscopy. The FeII content in the un-doped iron phosphate glass and barium doped iron phosphate glasses was 20, 21 and 22 ± 1% respectively and the average Fe coordination varied from 5.3 ± 0.2 to 5.7 ± 0.2 with increasing Ba content. The atomic scale structure was further probed by Fe K-edge X-ray absorption spectroscopy. The average coordination number provided by extended X-ray absorption fine structure spectroscopy and X-ray absorption near edge structure was in good agreement with that given by the Mössbauer data.

Basaltic glass alteration in confined media: analogy with nuclear glass in geological disposal conditions

International Nuclear Information System (INIS)

Parruzot, Benjamin

2014-01-01

This dissertation concerns basaltic glass alteration mechanisms and rates. Through a better understanding of the processes controlling the basaltic glass durability, this thesis attempts to establish a link between laboratory studies and volcanic glass alteration in natural environment. The methodology used here is similar to the one used for nuclear glasses. Thus, we measured for the first time the residual alteration rate of basaltic glasses. Protective effect of the alteration film is clearly established. Moreover, synthetic glass representativeness is evaluated through a study focused on the effect of iron oxidation degree on the glass structure and leaching properties. A minor effect of Fe II on the forward rate and a negligible effect on the residual rate are shown. The residual rate is extrapolated at 5 C and compared to the mean alteration rate of natural samples of ages ranging from 1900 to 10 7 years. Non-zeolitized natural glasses follow this linear tendency, suggesting a control of the long-term rate by clayey secondary phase precipitation. Natural environments are open environments: a parametric study was performed in order to quantify the water flow rate effect on chemical composition of the alteration layer. When applied to two natural samples, the obtained laws provide coherent results. It seems possible to unify the descriptive approach from the study of natural environments to the mechanistic approach developed at the laboratory. The next step will consist in developing a model to transpose these results to nuclear glasses. (author) [fr

Tin( ii ) ketoacidoximates: synthesis, X-ray structures and processing to tin( ii ) oxide

KAUST Repository

Khanderi, Jayaprakash; Davaasuren, Bambar; Alshankiti, Buthainah; Rothenberger, Alexander

2015-01-01

to spherical SnO particles of size 10-500 nm. Spin coating of 1 on Si or a glass substrate followed by heating at 200 °C results in a uniform film of SnO. The band gap of the produced SnO film and nanomaterial was determined by diffuse reflectance spectroscopy

Optical characterization and blu-ray recording properties of metal(II) azo barbituric acid complex films

Energy Technology Data Exchange (ETDEWEB)

Li, X.Y. [Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)], E-mail: xyli@siom.ac.cn; Wu, Y.Q. [Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Key Lab of Functional Inorganic Material Chemistry (Heilongjiang University), Ministry of Education, Haerbin 150080 (China)], E-mail: yqwu@siom.ac.cn; Gu, D.D.; Gan, F.X. [Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)

2009-02-25

Smooth thin films of nickel(II), cobalt(II) and zinc(II) complexes with azo barbituric acid were prepared by the spin-coating method. Absorption spectra of the thin films on K9 glass substrates in 300-700 nm wavelength region were measured. Optical constants (complex refractive index N = n + ik) of the thin films prepared on single-crystal silicon substrates in 275-695 nm wavelength region were investigated on rotating analyzer-polarizer type of scanning ellipsometer, and dielectric constant {epsilon} ({epsilon} = {epsilon}{sub 1} + i{epsilon}{sub 2}) as well as absorption coefficient {alpha} of thin films were calculated at 405 nm. In addition, static optical recording properties of the cobalt(II) complex thin film with an Ag reflective layer was carried out using a 406.7 nm blue-violet laser and a high numerical aperture (NA) of 0.90. Clear recording marks with high reflectivity contrast (>60%) at proper laser power and pulse width were obtained, and the size of recording mark was as small as 250 nm. The results indicate that these metal(II) complexes are promising organic recording medium for the blu-ray optical storage system.

Neodymium partitioning in zirconolite-based glass-ceramics designed for minor actinides immobilization

International Nuclear Information System (INIS)

Loiseau, P.; Caurant, D.; Baffier, N.; Fillet, C.

2000-01-01

This study deals with glass-ceramic matrices designed for the conditioning of minor actinides, in which zirconolite crystals (CaZrTi 2 O 7 ) are homogeneously dispersed in a residual glassy matrix. Good immobilization performances require a high enrichment of actinides in the crystalline phase (double containment principle). Glass-ceramics are obtained by controlled devitrification of an aluminosilicate parent glass containing large amounts of TiO 2 and ZrO 2 . Neodymium was selected to simulate the trivalent minor actinides. Crystallization was performed at 1200 deg. C for various Nd 2 O 3 contents (0 - 10 wt. %). In all cases, zirconolite crystallization is obtained in the bulk of glass-ceramics. The evolution of Nd 3+ location between the crystals and the residual glass was followed by electron spin resonance and optical absorption. Both techniques demonstrate that neodymium is partly incorporated in zirconolite crystals. Moreover, total Nd 2 O 3 content in parent glass has a strong effect on Nd 3+ ions distribution. (authors)

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...

Spin crossover behaviour in Hofmann-like coordination polymer Fe(py)2[Pd(CN)4] with 57Fe Mössbauer spectra

Science.gov (United States)

Kitazawa, Takafumi; Kishida, Takanori; Kawasaki, Takeshi; Takahashi, Masashi

2017-11-01

We have prepared the 2D spin crossover complexes Fe(L)2Pd(CN)4 (L = py : 1a; py-D5 : 1b and py-15N : 1c). 1a has been characterised by 57Fe Mossbauer spectroscopic measurements, single crystal X-ray determination and SQUID measurements. The Mössbauer spectra for 1a indicate that the iron(II) spin states are in high spin states at 298 K and are in low spin states at 77 K. The crystal structures of 1a at 298 K and 90 K also show the high spin state and the low spin state respectively, associated with the Fe(II)-N distances. The spin transition temperature range of 1a is higher than that of Fe(py)2Ni(CN)4 since Pd(II) ions are larger and heavier than Ni(II) ions. SQUID data indicate isotope effects among 1a, 1b and 1c are observed in very small shifts of the transition temperatures probably due to larger and heavier Pd(II) ions. The delicate shifts would be associated with subtle balances between different vibrations around Fe(II) atoms and electronic factors.

Charge and Spin Transport in Spin-orbit Coupled and Topological Systems

KAUST Repository

Ndiaye, Papa Birame

2017-10-31

In the search for low power operation of microelectronic devices, spin-based solutions have attracted undeniable increasing interest due to their intrinsic magnetic nonvolatility. The ability to electrically manipulate the magnetic order using spin-orbit interaction, associated with the recent emergence of topological spintronics with its promise of highly efficient charge-to-spin conversion in solid state, offer alluring opportunities in terms of system design. Although the related technology is still at its infancy, this thesis intends to contribute to this engaging field by investigating the nature of the charge and spin transport in spin-orbit coupled and topological systems using quantum transport methods. We identified three promising building blocks for next-generation technology, three classes of systems that possibly enhance the spin and charge transport efficiency: (i)- topological insulators, (ii)- spin-orbit coupled magnonic systems, (iii)- topological magnetic textures (skyrmions and 3Q magnetic state). Chapter 2 reviews the basics and essential concepts used throughout the thesis: the spin-orbit coupling, the mathematical notion of topology and its importance in condensed matter physics, then topological magnetism and a zest of magnonics. In Chapter 3, we study the spin-orbit torques at the magnetized interfaces of 3D topological insulators. We demonstrated that their peculiar form, compared to other spin-orbit torques, have important repercussions in terms of magnetization reversal, charge pumping and anisotropic damping. In Chapter 4, we showed that the interplay between magnon current jm and magnetization m in homogeneous ferromagnets with Dzyaloshinskii-Moriya (DM) interaction, produces a field-like torque as well as a damping-like torque. These DM torques mediated by spin wave can tilt the imeaveraged magnetization direction and are similar to Rashba torques for electronic systems. Moreover, the DM torque is more efficient when magnons are

Magnetism of one-dimensional strongly repulsive spin-1 bosons with antiferromagnetic spin-exchange interaction

International Nuclear Information System (INIS)

Lee, J. Y.; Guan, X. W.; Batchelor, M. T.; Lee, C.

2009-01-01

We investigate magnetism and quantum phase transitions in a one-dimensional system of integrable spin-1 bosons with strongly repulsive density-density interaction and antiferromagnetic spin-exchange interaction via the thermodynamic Bethe ansatz method. At zero temperature, the system exhibits three quantum phases: (i) a singlet phase of boson pairs when the external magnetic field H is less than the lower critical field H c1 ; (ii) a ferromagnetic phase of atoms in the hyperfine state |F=1, m F =1> when the external magnetic field exceeds the upper critical field H c2 ; and (iii) a mixed phase of singlet pairs and unpaired atoms in the intermediate region H c1 c2 . At finite temperatures, the spin fluctuations affect the thermodynamics of the model through coupling the spin bound states to the dressed energy for the unpaired m F =1 bosons. However, such spin dynamics is suppressed by a sufficiently strong external field at low temperatures. Thus the singlet pairs and unpaired bosons may form a two-component Luttinger liquid in the strong coupling regime.

Comparative Evaluation of the Antimicrobial Properties of Glass Ionomer Cements with and without Chlorhexidine Gluconate.

Science.gov (United States)

Yadiki, Josna Vinutha; Jampanapalli, Sharada Reddy; Konda, Suhasini; Inguva, Hema Chandrika; Chimata, Vamsi Krishna

2016-01-01

Chlorhexidine gluconate is a widely used antimicrobial agent. Adding chlorhexidine and quaternary ammonium compounds to filling materials, such as composite resins, acrylic resins, and glass ionomer cements increases the antibacterial property of restorative materials. This study includes antibacterial property of glass ionomer restorative cements with chlorhexidine gluconate. The primary objective of our study was to compare the antimicrobial properties of two commercially available glass ionomer cements with and without chlorhexidine gluconate on strains of mutans streptococci. Two glass ionomers (Fuji II Conventional and Fuji IX) were used. Chlorhexidine gluconate was mixed with glass ionomer cements, and antimicrobial properties against mutans streptococci were assessed by agar diffusion. The tested bacterial strain was inhibited and the antimicrobial properties decreased with time. The highest amount of antimicrobial activity with mean inhibitory zone was found in Fuji II with chlorhexidine gluconate followed by Fuji IX with chlorhexidine gluconate, Fuji II without chlorhexidine gluconate, and Fuji IX without chlorhexidine gluconate. The results of the study confirmed that the addition of 5% chlorhexidine gluconate to Fuji II and Fuji IX glass ionomer cements resulted in a restorative material that had increased antimicrobial properties over the conventional glass ionomer cements alone for Streptococcus mutans. How to cite this article: Yadiki JV, Jampanapalli SR , Konda S, Inguva HC, Chimata VK. Comparative Evaluation of the Antimicrobial Properties of Glass Ionomer Cements with and without Chlorhexidine Gluconate. Int J Clin Pediatr Dent 2016;9(2):99-103.

Effect of Si on the glass-forming ability, thermal stability and magnetic properties of Fe-Co-Zr-Mo-W-B alloys

Energy Technology Data Exchange (ETDEWEB)

Wang, W.-M. [Institute for Metallic Materials, IFW Dresden, P.O. 270016, Dresden D-01171 (Germany); Key Lab of Liquid Structure and Heredity of Materials, Shandong University, Jinan 250061 (China); Gebert, A. [Institute for Metallic Materials, IFW Dresden, P.O. 270016, Dresden D-01171 (Germany)], E-mail: a.gebert@ifw-dresden.de; Roth, S.; Kuehn, U.; Schultz, L. [Institute for Metallic Materials, IFW Dresden, P.O. 270016, Dresden D-01171 (Germany)

2008-07-14

This paper presents investigations on the effect of Si on the glass-forming ability, thermal stability and magnetic properties of the Fe-Co-Zr-Mo-W-B samples (group I: Fe{sub 60}Co{sub 8}Zr{sub 10}Mo{sub 5}W{sub 2}B{sub 15-x}Si{sub x}, 1 {<=} x {<=} 4; group II: Fe{sub 60}Co{sub 8}Zr{sub 10-x}Mo{sub 5}W{sub 2}B{sub 15}Si{sub x}, 0 {<=} x {<=} 4; group III: Fe{sub 60}Co{sub 8}Zr{sub 8}Mo{sub 5}W{sub 2}B{sub 17-x}Si{sub x}, 0 {<=} x {<=} 2) prepared by melt spinning, injection casting, and centrifugal casting methods. It is found that the glass-forming ability (GFA) of the alloys in group I is more deteriorated than that in group II, and that the alloys in group III can be cast into the rods of 1-3 mm diameter without crystalline reflections in their XRD patterns. For the amorphous ribbons and rods, a non-monotonic change of the nearest neighbour distance r{sub 1} with increasing Si content c{sub Si} was detected, which is parallel to that of the glass transition and crystallization temperatures T{sub g} and T{sub x}, but opposite to that of the magnetization at room temperature M{sub RT} and the Curie temperature T{sub c}. This correlation can be interpreted by a structure model presuming that iron atoms appear simultaneously in two types of local structures in the amorphous samples.

Acoustically induced spin transport in (110)GaAs quantum wells

Energy Technology Data Exchange (ETDEWEB)

Couto, Odilon D.D. Jr.

2008-09-29

In this work, we employ surface acoustic waves (SAWs) to transport and manipulate optically generated spin ensembles in (110) GaAs quantum wells (QWs). The strong carrier confinement into the SAW piezoelectric potential allows for the transport of spin-polarized carrier packets along well-defined channels with the propagation velocity of the acoustic wave. In this way, spin transport over distances exceeding 60 m is achieved, corresponding to spin lifetimes longer than 20 ns. The demonstration of such extremely long spin lifetimes is enabled by three main factors: (i) Suppression of the D'yakonov-Perel' spin relaxation mechanism for z-oriented spins in (110) IIIV QWs; (ii) Suppression of the Bir-Aronov-Pikus spin relaxation mechanism caused by the type-II SAW piezoelectric potential; (iii) Suppression of spin relaxation induced by the mesoscopic carrier confinement into narrow stripes along the SAW wave front direction. A spin transport anisotropy under external magnetic fields (B{sub ext}) is demonstrated for the first time. Employing the well-defined average carrier momentum impinged by the SAW, we analyze the spin dephasing dynamics during transport along the [001] and [1 anti 10] in-plane directions. For transport along [001], fluctuations of the internal magnetic field (B{sub int}), which arises from the spin-orbit interaction associated with the bulk inversion asymmetry of the crystal, lead to decoherence within 2 ns as the spins precess around B{sub ext}. In contrast, for transport along the [1 anti 10] direction, the z-component of the spin polarization is maintained for times one order of magnitude longer due to the non-zero average value of B{sub int}. The dephasing anisotropy between the two directions is fully understood in terms of the dependence of the spin-orbit coupling on carrier momentum direction, as predicted by the D'yakonov-Perel' mechanism for the (110) system. (orig.)

Experimental analysis of the production of micro- and nanofibres by Laser Spinning

International Nuclear Information System (INIS)

Quintero, F.; Pou, J.; Lusquinos, F.; Riveiro, A.

2007-01-01

Laser Spinning is a new technique for the production of glass fibres with diameters in the nanometre to micrometre scale. It allows large quantities of nanofibres to be made with specific, controllable chemical compositions. Furthermore, the production of amorphous micro- and nanofibres of non-ready glass former materials was demonstrated. All these novel characteristics will potentially open up a whole new range of applications for the fibres. In this technique a high power laser is employed to melt the precursor solid material, while a supersonic gas jet is injected into the melt volume. The melt forms glass fibres as a result of its viscous elongation and cooling by the drag force and convective heat transfer produced by the gas jet. The influence of several operating conditions controlling the morphology, composition, and diameter distribution of the fibres is experimentally assessed by means of electron microscopy analysis, X-ray fluorescence and time-of-flight secondary ion mass spectrometry. The experimental results are discussed based on a theoretical explanation of the process of fibre formation. This leads ultimately to the deduction of a set of rules regarding the influence of the factors studied on the production of nanofibres by Laser Spinning

Spinor monopole harmonics and the Pauli spin equation

International Nuclear Information System (INIS)

Pereira, J.G.; Ferreira, P.L.

1982-01-01

In the framework of Wu and Yang theory of U(1) magnetic monopoles, two problems are revisited: (i) the binding of spin-0 monopole to a spin-1/2 particle possessing an arbitrary magnetic dipole moment, and (ii) the energy levels and properties of the electron-dyon system. In both problems, the spin-1/2 particle is assumed to obey the Pauli spin equation. Spin-orbit and other higher order terms are treated as a perturbation, in connection with the second mentioned problem. Wu and Yang's spinor monopole harmonics allow an elegant and simplified treatment of those problems. The results obtained are in good agreement with those obtained in older papers. (Author) [pt

Copper oxide thin films anchored on glass substrate by sol gel spin coating technique

Science.gov (United States)

Krishnaprabha, M.; Venu, M. Parvathy; Pattabi, Manjunatha

2018-05-01

Owing to the excellent optical, thermal, electrical and photocatalytic properties, copper oxide nanoparticles/films have found applications in optoelectronic devices like solar/photovoltaic cells, lithium ion batteries, gas sensors, catalysts, magnetic storage media etc. Copper oxide is a p-type semiconductor material having a band gap energy varying from 1.2 eV-2.1 eV. Syzygium Samarangense fruit extract was used as reducing agent to synthesize copper oxide nanostructures at room temperature from 10 mM copper sulphate pentahydrate solution. The synthesized nanostructures are deposited onto glass substrate by spin coating followed by annealing the film at 200 °C. Both the copper oxide colloid and films are characterized using UV-Vis spectroscopy, field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS) techniques. Presence of 2 peaks at 500 nm and a broad peak centered around 800 nm in the UV-Vis absorbance spectra of copper oxide colloid/films is indicative of the formation of anisotropic copper oxide nanostructures is confirmed by the FESEM images which showed the presence of triangular shaped and rod shaped particles. The rod shaped particles inside island like structures were found in unannealed films whereas the annealed films contained different shaped particles with reduced sizes. The elemental analysis using EDS spectra of copper oxide nanoparticles/films showed the presence of both copper and oxygen. Electrical properties of copper oxide nanoparticles are affected due to quantum size effect. The electrical studies carried out on both unannealed and annealed copper oxide films revealed an increase in resistivity with annealing of the films.

Static and dynamic spin fluctuations in the spin glass doping regime in La2-xSrxCuO4+y

International Nuclear Information System (INIS)

Birgeneau, R.J.; Belk, N.; Kastner, M.A.; Keimer, B.; Shirane, G.

1991-01-01

We review the results of neutron scattering studies of the static and dynamic spin fluctuations crystals of La 2-x Sr x CuO 4+δ in the doping regime intermediate between the Neel and superconducting regions. In this regime the in-plane resistance is linear in temperature down to ∼80 K with a crossover due to logarithmic conductance effects at lower temperatures. The static spin correlations are well-described by a simple model in which the inverse correlation length κ(x,T) =κ(x,0) + κ(0,T). The most dramatic new result is the discovery by Keimer et al. that the dynamic spin fluctuations exhibit a temperature dependence which is a simple function of ω/T for temperatures 10 K≤T≤500 K for a wide range of energies. This scaling leads to a natural explanation of a variety of normal state properties of the copper oxides. 21 refs., 4 figs

Tin( ii ) ketoacidoximates: synthesis, X-ray structures and processing to tin( ii ) oxide

KAUST Repository

Khanderi, Jayaprakash

2015-10-21

Tin(ii) ketoacidoximates of the type [HONCRCOO]Sn (R = Me 1, CHPh 2) and (MeONCMeCOO)Sn] NH·2HO 3 were synthesized by reacting pyruvate- and hydroxyl- or methoxylamine RONH (R = H, Me) with tin(ii) chloride dihydrate SnCl·2HO. The single crystal X-ray structure reveals that the geometry at the Sn atom is trigonal bipyramidal in 1, 2 and trigonal pyramidal in 3. Inter- or intramolecular hydrogen bonding is observed in 1-3. Thermogravimetric (TG) analysis shows that the decomposition of 1-3 to SnO occurs at ca. 160 °C. The evolved gas analysis during TG indicates complete loss of the oximato ligand in one step for 1 whereas a small organic residue is additionally removed at temperatures >400 °C for 2. Above 140 °C, [HONC(Me)COO]Sn (1) decomposes in air to spherical SnO particles of size 10-500 nm. Spin coating of 1 on Si or a glass substrate followed by heating at 200 °C results in a uniform film of SnO. The band gap of the produced SnO film and nanomaterial was determined by diffuse reflectance spectroscopy to be in the range of 3.0-3.3 eV. X-ray photoelectron spectroscopy indicates surface oxidation of the SnO film to SnO in ambient atmosphere.

Non-linear spin transport in magnetic semiconductor superlattices

International Nuclear Information System (INIS)

Bejar, Manuel; Sanchez, David; Platero, Gloria; MacDonald, A.H.

2004-01-01

The electronic spin dynamics in DC-biased n-doped II-VI semiconductor multiquantum wells doped with magnetic impurities is presented. Under certain range of electronic doping, conventional semiconductor superlattices present self-sustained oscillations. Magnetically doped wells (Mn) present large spin splittings due to the exchange interaction. The interplay between non-linear interwell transport, the electron-electron interaction and the exchange between electrons and the magnetic impurities produces interesting time-dependent features in the spin polarization current tuned by an external magnetic field

Antibacterial effect of bioactive glasses on clinically important anaerobic bacteria in vitro.

Science.gov (United States)

Leppäranta, Outi; Vaahtio, Minna; Peltola, Timo; Zhang, Di; Hupa, Leena; Hupa, Mikko; Ylänen, Heimo; Salonen, Jukka I; Viljanen, Matti K; Eerola, Erkki

2008-02-01

Bioactive glasses (BAGs) of different compositions have been studied for decades for clinical use and they have found many dental and orthopaedic applications. Particulate BAGs have also been shown to have antibacterial properties. This large-scale study shows that two bioactive glass powders (S53P4 and 13-93) and a sol-gel derived material (CaPSiO II) have an antibacterial effect on 17 clinically important anaerobic bacterial species. All the materials tested demonstrated growth inhibition, although the concentration and time needed for the effect varied depending on the BAG. Glass S53P4 had a strong growth-inhibitory effect on all pathogens tested. Glass 13-93 and sol-gel derived material CaPSiO II showed moderate antibacterial properties.

Homogeneous-inhomogeneous models of Ag x (Ge0.25Se0.75)100-x bulk glasses

International Nuclear Information System (INIS)

Arcondo, B.; Urena, M.A.; Piarristeguy, A.; Pradel, A.; Fontana, M.

2007-01-01

Ge-Se system presents an extensive glass forming composition range even when different metals (Ag, Sb, Bi) are added. In spite that the addition of Ag (up to 30 at%) to Ge-Se does not affect substantially the glass forming tendency, it impacts significantly on the transport properties. (Ge 0.25 Se 0.75 ) 100- x Ag x is a fast ionic conductor with x≥8 at% whereas it is a semiconductor for x 0.25 Se 0.75 ) 100- x Ag x bulk samples. These results appear to sustain this model. However previous structural and thermal studies oppose it. Moessbauer spectrometry on samples (0≤x≤25) containing 0.5 at% of 57 Fe is performed at T≤300 K. The main contribution to the glasses spectra correspond to low spin Fe 2+ in octahedral coordination and high spin Fe 2+ in distorted octahedral environments. The relative population of both sites changes continuously as Ag concentration varies denoting that the change in the transport behavior obeys to a percolation phenomenon. The low temperature results are discussed with the aim to throw light on the controversy about the homogeneity-inhomogeneity of the studied bulk glasses

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

International Nuclear Information System (INIS)

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

1997-01-01

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

A Moessbauer spectroscopic study of stannosilicate and ferrisilicate glasses

International Nuclear Information System (INIS)

Appleyard, P.G.

2000-02-01

Silicate glasses of variable composition, containing tin and iron have been studied using Moessbauer spectroscopy. The glass samples consisted of 3 basic groups; binary stannosilicate glasses, ternary stannosilicate glasses and ternary ferrisilicate glasses. The binary stannosilicate glasses were a simple x SnO + (1-x) SiO 2 composition, with x ranging from 16.5% to 67.7% mole. The ternary stannosilicate glasses followed a nominal compositional range of 0.5 SiO 2 + (0.5-x) SnO + x RO, where RO is modifier oxide. Several series of ternary stannosilicates were manufactured, with each series containing a different modifier type. The modifiers chosen were; group I metal oxides of Li, Na, K and Rb, group II metal oxides of Mg, Ca and Sr and group III metal oxide of Al. Two series of ternary ferrisilicate glasses were manufactured following nominal compositional ranges of (0.7-x) SiO 2 + x Fe 2 O 3 + 0.3 Na 2 O and 0.7 SiO 2 + xFe 2 O 3 + (0.3-x) Na 2 O. In the majority of the stannosilicate glasses, the Sn was shown to exist primarily in the Sn(II) valence state. The Moessbauer centre shift and quadrupole splitting of the Sn(II) were shown to possess a dependence on sample concentration, this being weak in the binary glasses, but large and distinct in the ternary glasses. The isomer shift and quadrupole splitting slowly decreased with increasing modifier concentration in the ternary glasses. The rate of this decrease was proportional to the Z/radius of the modifier ion. Variable temperature experiments on a large selection of the glasses revealed that the Sn(II) isomer shift and quadrupole splitting possessed positive and negative dependencies on temperature respectively. The increase in isomer shift is consistent with the effects of thermal expansion and an increase in pressure at the Sn site. The decrease in quadrupole splitting is also consistent with thermal expansion of the Sn-O bonds. The temperature dependence of the isomer shift was incorporated into the

Electron spin-lattice relaxation mechanisms of radiation produced trapped electrons and hydrogen atoms in aqueous and organic glassy matrices. Modulation of electron nuclear dipolar interaction by tunnelling modes in a glassy matrix. [. gamma. rays

Energy Technology Data Exchange (ETDEWEB)

Bowman, M K; Kevan, L [Wayne State Univ., Detroit, Mich. (USA). Dept. of Chemistry

1977-01-01

The spin lattice relaxation of trapped electrons in aqueous and organic glasses and trapped hydrogen atoms in phosphoric acid glass has been directly studied as a function of temperature by the saturation recovery method. Below 50 to 100 K, the major spin lattice relaxation mechanism involves modulation of the electron nuclear dipolar (END) interaction with nuclei in the radical's environment by tunnelling of those nuclei between two or more positions. This relaxation mechanism occurs with high efficiency and has a characteristic linear temperature dependence. The tunnelling nuclei around trapped electrons do not seem to involve the nearest neighbor nuclei which are oriented by the electron in the process of solvation. Instead the tunnelling nuclei typically appear to be next nearest neighbors to the trapped electron. The identities of the tunnelling nuclei have been deduced by isotopic substitution and are attributed to: Na in 10 mol dm/sup -3/ NaOH aqueous glass, ethyl protons in ethanol glass, methyl protons in methanol glass and methyl protons in MTHF glass. For trapped hydrogen atoms in phosphoric acid, the phosphorus nuclei appear to be the effective tunnelling nuclei. Below approximately 10 K the spin lattice relaxation is dominated by a temperature independent cross relaxation term for H atoms in phosphoric acid glass and for electrons in 10 mol dm/sup -3/ NaOH aqueous glass, but not for electrons in organic glasses. This is compared with recent electron-electron double resonance studies of cross relaxation in these glasses. The spin lattice relaxation of O/sup -/ formed in 10 mol dm/sup -3/ NaOH aqueous glass was also studied and found to be mainly dominated by a Raman process with an effective Debye temperature of about 100 K.

pH-Dependent spin state population and 19F NMR chemical shift via remote ligand protonation in an iron(ii) complex.

Science.gov (United States)

Gaudette, Alexandra I; Thorarinsdottir, Agnes E; Harris, T David

2017-11-30

An Fe II complex that features a pH-dependent spin state population, by virtue of a variable ligand protonation state, is described. This behavior leads to a highly pH-dependent 19 F NMR chemical shift with a sensitivity of 13.9(5) ppm per pH unit at 37 °C, thereby demonstrating the potential utility of the complex as a 19 F chemical shift-based pH sensor.

Relativistic description of quark-antiquark bound states. II. Spin-dependent treatment

International Nuclear Information System (INIS)

Gara, A.; Durand, B.; Durand, L.

1990-01-01

We present the results of a study of light- and heavy-quark--antiquark bound states in the context of the reduced Bethe-Salpeter equation, including the full spin dependence. We obtain good fits to the observed spin splittings in the b bar b and c bar c systems using a short-distance single-gluon-exchange interaction, and a long-distance scalar confining interaction. However, we cannot obtain satisfactory fits to the centers of gravity of the b bar b and c bar c spin multiplets at the same time, and the splittings calculated for q bar Q mesons containing the lighter quarks are very poor. The difficulty appears to be intrinsic to the reduced Salpeter equation for reasons which we discuss

Characterization and Conduction Mechanism of Highly Conductive Vanadate Glass

Directory of Open Access Journals (Sweden)

Tetsuaki Nishida

2015-12-01

Full Text Available This paper reviews recent studies of highly conductive barium iron vanadate glass with a composition of 20 BaO ∙ 10 Fe2O3 ∙ 70 V2O5 (in mol %. Isothermal annealing of the vanadate glass for several ten minutes at a given temperature, higher than glass transition temperature or crystallization temperature, caused an increase in σ. Substitution of CuI (3d10, ZnII (3d10 and CuII (3d9 for FeIII (3d5 was investigated to elucidate the effect of electron configuration on the conductivity (σ. A marked decrease in the activation energy of conduction (Ea was also observed after the annealing. Values of Ea were correlated to the energy gap between the donor level and the conduction band (CB in the n-type semiconductor model. Isothermal annealing of ZnII-substituted vanadate glass (20 BaO ∙ 5 ZnO ∙ 5 Fe2O3 ∙ 70 V2O5 at 450 °C for 30 min showed an increase in σ from 2.5 × 10–6 to 2.1 × 10–1 S cm–1, which was one order of magnitude larger than that of non-substituted vanadate glass (3.4 × 10–2 S cm–1. Under the same annealing condition, σ’s of 2.0 × 10–1 and 3.2 × 10–1 S cm–1 were observed for 20 BaO ∙ 5 Cu2O ∙ 5 Fe2O3 ∙ 70 V2O5 and 20 BaO ∙ 5 CuO ∙ 5 Fe2O3 ∙ 70 V2O5 glasses, respectively. These results demonstrate an increase in the carrier (electron density in the CB, primarily composed of anti-bonding 4s-orbitals.

CONDENSED MATTER: STRUCTURE, MECHANICAL, AND THERMAL PROPERTIES: Observation of β-Relaxation in Sub-Tg Isothermally Annealed Al-Based Metallic Glasses

Science.gov (United States)

Yang, Hong-Wang; Tong, Wei-Ping; Zhao, Xiang; Zuo, Liang; Wang, Jian-Qiang

2008-09-01

Al85 Ni5 Y8 C02 and Al 85 Ni5 Y6 C02 Fe2 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.

Silica nanoparticles on front glass for efficiency enhancement in superstrate-type amorphous silicon solar cells

Science.gov (United States)

Das, Sonali; Banerjee, Chandan; Kundu, Avra; Dey, Prasenjit; Saha, Hiranmay; Datta, Swapan K.

2013-10-01

Antireflective coating on front glass of superstrate-type single junction amorphous silicon solar cells (SCs) has been applied using highly monodispersed and stable silica nanoparticles (NPs). The silica NPs having 300 nm diameter were synthesized by Stober technique where the size of the NPs was controlled by varying the alcohol medium. The synthesized silica NPs were analysed by dynamic light scattering technique and Fourier transform infrared spectroscopy. The NPs were spin coated on glass side of fluorinated tin oxide (SnO2: F) coated glass superstrate and optimization of the concentration of the colloidal solution, spin speed and number of coated layers was done to achieve minimum reflection characteristics. An estimation of the distribution of the NPs for different optimization parameters has been done using field-emission scanning electron microscopy. Subsequently, the transparent conducting oxide coated glass with the layer having the minimum reflectance is used for fabrication of amorphous silicon SC. Electrical analysis of the fabricated cell indicates an improvement of 6.5% in short-circuit current density from a reference of 12.40 mA cm-2 while the open circuit voltage and the fill factor remains unaltered. A realistic optical model has also been proposed to gain an insight into the system.

Silica nanoparticles on front glass for efficiency enhancement in superstrate-type amorphous silicon solar cells

International Nuclear Information System (INIS)

Das, Sonali; Kundu, Avra; Dey, Prasenjit; Saha, Hiranmay; Datta, Swapan K; Banerjee, Chandan

2013-01-01

Antireflective coating on front glass of superstrate-type single junction amorphous silicon solar cells (SCs) has been applied using highly monodispersed and stable silica nanoparticles (NPs). The silica NPs having 300 nm diameter were synthesized by Stober technique where the size of the NPs was controlled by varying the alcohol medium. The synthesized silica NPs were analysed by dynamic light scattering technique and Fourier transform infrared spectroscopy. The NPs were spin coated on glass side of fluorinated tin oxide (SnO 2 : F) coated glass superstrate and optimization of the concentration of the colloidal solution, spin speed and number of coated layers was done to achieve minimum reflection characteristics. An estimation of the distribution of the NPs for different optimization parameters has been done using field-emission scanning electron microscopy. Subsequently, the transparent conducting oxide coated glass with the layer having the minimum reflectance is used for fabrication of amorphous silicon SC. Electrical analysis of the fabricated cell indicates an improvement of 6.5% in short-circuit current density from a reference of 12.40 mA cm −2 while the open circuit voltage and the fill factor remains unaltered. A realistic optical model has also been proposed to gain an insight into the system. (paper)

Synthesis of glass-ceramics using glass cullet and vitrified industrial by-products

Energy Technology Data Exchange (ETDEWEB)

Karamberi, A.; Orkopoulos, K.; Moutsatsou, A. [National Technical University of Athens, Athens (Greece)

2007-07-01

This study concerns the recycling of inorganic waste materials for the production of glass-ceramics and the evaluation of the developed physical properties. Four industrial by-products were selected due to their mass production: (I) two high calcium lignite fly ashes, (ii) slag derived from the production of Fe-Ni and, (iii) steel slag. In order to examine the role of the SiO{sub 2} in the crystallization process, glass cullet and Egyptian sand were added. Thermal treatment, at 1450{sup o}C, enables the production of glasses using mixtures of these materials at appropriate proportions. The crystallization was achieved by heating at 900, 950 and 1000{sup o}C. The produced materials were examined concerning their structure by X-ray diffraction and scanning electron microscopy (SEM-EDS). The results showed that the crystalline phase is greatly depending on the structure of the raw material and the thermal process, influencing accordingly the hardness of the final products.

cobalt(II), nickel(II)

Indian Academy of Sciences (India)

Unknown

procedures. The supporting electrolyte, NaClO4 used in the voltammetric experiment was purchased from. Sigma. IR spectra were recorded in KBr medium on .... (13⋅6). L = Schiff base ligand form of one broad band envelope. The electronic spectra of Co(II) complex showed two spin-allowed transitions at 17856 and ...

Glass composition and solution speciation effects on stage III dissolution

International Nuclear Information System (INIS)

Trivelpiece, Cory L.; Rice, Jarret A.; Pantano, Carlo G.

2017-01-01

To understand and mitigate the onset of Stage III corrosion of multicomponent oxides waste glasses. Stage III refers to a resumption of the high initial rate of glass dissolution in some glass samples that have otherwise exhibited dissolution at the much lower residual rate for a long time (Stage II). Although the onset of Stage III is known to occur concurrently with the precipitation of particular alteration products, the root cause of the transition is still unknown. Certain glass compositions (notably AFCI) and high pH environmental conditions are also associated with this observed transition.

Glass composition and solution speciation effects on stage III dissolution

Energy Technology Data Exchange (ETDEWEB)

Trivelpiece, Cory L. [Pennsylvania State Univ., University Park, PA (United States); Rice, Jarret A. [Pennsylvania State Univ., University Park, PA (United States); Pantano, Carlo G. [Pennsylvania State Univ., University Park, PA (United States)

2017-10-03

To understand and mitigate the onset of Stage III corrosion of multicomponent oxides waste glasses. Stage III refers to a resumption of the high initial rate of glass dissolution in some glass samples that have otherwise exhibited dissolution at the much lower residual rate for a long time (Stage II). Although the onset of Stage III is known to occur concurrently with the precipitation of particular alteration products, the root cause of the transition is still unknown. Certain glass compositions (notably AFCI) and high pH environmental conditions are also associated with this observed transition.

Photovoltaic Properties of Co-doped ZnO Thin Film on Glass Substrate

International Nuclear Information System (INIS)

Sabia Aye; Zin Ma Ma; May Nwe Oo; Than Than Win; Yin Maung Maung; Ko Ko Kyaw Soe

2011-12-01

Cobalt (Co) 0.4 mol doped zinc oxide (ZnO) fine powder was prepared by solid state mixed oxide route. Phase formation and crystal structure of Co-doped ZnO (CZO) powder were examined by X-ray diffraction (XRD). Scanning Electron Microscopy (SEM) was used to observe the micro structure of Co doped ZnO powder. Energy Dispersive X-ray Fluorescent (EDXRF) technique gave the elemental content of cobalt and zinc. Co-doped ZnO film was formed on glass substrate by spin coating technique. Photovoltaic properties of CZO/glass cell were measured.

Asymmetric electroresistance of cluster glass state in manganites

KAUST Repository

Lourembam, James

2014-03-31

We report the electrostatic modulation of transport in strained Pr0.65(Ca0.75Sr0.25)0.35MnO3 thin films grown on SrTiO3 by gating with ionic liquid in electric double layer transistors (EDLT). In such manganite films with strong phase separation, a cluster glass magnetic state emerges at low temperatures with a spin freezing temperature of about 99 K, which is accompanied by the reentrant insulating state with high resistance below 30 K. In the EDLT, we observe bipolar and asymmetric modulation of the channel resistance, as well as an enhanced electroresistance up to 200% at positive gate bias. Our results provide insights on the carrier-density-dependent correlated electron physics of cluster glass systems.

NMR in metal cluster compounds compared to glasses

International Nuclear Information System (INIS)

Staveren, M.P.J. van; Brom, H.B.; Jongh, L.J. de; Schmid, G.

1991-01-01

The field and temperature dependence of the 31 P nuclear spin lattice relaxation rate in the metal cluster compound Ru 55 (P(t-Bu) 3 ) 12 Cl 20 follows a power law: 1/T 1 ∝ T n B -m , with n = 1.5 ± 0.1 at 3.25 T and n = 1.3 ± 0.1 at 6.45 T; m ≅ 1.4. Such dependences have so far only been observed in inorganic glasses and been attributed to two level systems. The correspondence suggests that the relaxation rate is due to interaction of the P-nuclear moment with electronic spins of stochastically moving charge carriers, which are thought to be responsible for the electrical conductivity through hopping between neigboring cluster molecules. (orig.)

Chemical modification of glass surface with a monolayer of nonchromophoric and chromophoric methacrylate terpolymer

Energy Technology Data Exchange (ETDEWEB)

Janik, Ryszard [Department of Polymer Engineering and Technology, Wroclaw University of Technology, 50-370 Wroclaw (Poland); Kucharski, Stanislaw, E-mail: stanislaw.kucharski@pwr.wroc.pl [Department of Polymer Engineering and Technology, Wroclaw University of Technology, 50-370 Wroclaw (Poland); Sobolewska, Anna [Institute of Physical and Theoretical Chemistry, Wroclaw University of Technology, 50-370 Wroclaw (Poland); Barille, Regis [Institut des Sciences et Techniques Moleculaires d' Angers ' Moltech Anjou' , CNRS UMR 6200, 49045 Angers (France)

2010-11-15

The methacrylate terpolymers, a nonchromophoric and chromophoric one, containing 2-hydroxyethyl groups were reacted with 3-isocyanatopropyltriethoxysilane to obtain reactive polymers able to form covalent bonding with -SiOH groups of the glass surface via triethoxysilane group condensation. Chemical modification of the Corning 2949 glass plates treated in this way resulted in increase of wetting angle from 11{sup o} to ca. 70-73{sup o}. Determination of ellipsometric parameters revealed low value of the substrate refractive index as compared with that of bulk Corning 2949 glass suggesting roughness of the surface. The AFM image of the bare glass surface and that modified with terpolymer monolayer confirmed this phenomenon. Modification of the glass with the terpolymer monolayer made it possible to create the substrate surface well suited for deposition of familiar chromophore film by spin-coating. The chromophore polymer film deposited onto the modified glass surface was found to be resistant to come unstuck in aqueous solution.

One-loop effective actions and higher spins. Part II

Science.gov (United States)

Bonora, L.; Cvitan, M.; Prester, P. Dominis; Giaccari, S.; Štemberga, T.

2018-01-01

In this paper we continue and improve the analysis of the effective actions obtained by integrating out a scalar and a fermion field coupled to external symmetric sources, started in the previous paper. The first subject we study is the geometrization of the results obtained there, that is we express them in terms of covariant Jacobi tensors. The second subject concerns the treatment of tadpoles and seagull terms in order to implement off-shell covariance in the initial model. The last and by far largest part of the paper is a repository of results concerning all two point correlators (including mixed ones) of symmetric currents of any spin up to 5 and in any dimensions between 3 and 6. In the massless case we also provide formulas for any spin in any dimension.

Self-cleaning glass coating containing titanium oxide and silicon

International Nuclear Information System (INIS)

Araujo, A.O. de; Alves, A.K.; Berutti, F.A.; Bergmann, C.P.

2009-01-01

Using the electro spinning technique nano fibers of titanium oxide doped with silicon were synthesized. As precursor materials, titanium propoxide, silicon tetra propoxide and a solution of polyvinylpyrrolidone were used. The non-tissue material obtained was characterized by X-ray diffraction to determine the phase and crystallite size, BET method to determine the surface and SEM to analyze the microstructure of the fibers. After ultrasound dispersion of this material in ethanol, the glass coatings were made by dip-coating methodology. The influence of the removal velocity, the solution composition and the glass surface preparation were evaluated. The film was characterized by the contact angle of a water droplet in its surface. (author)

Linear wide angle sun sensor for spinning satellites

Science.gov (United States)

Philip, M. P.; Kalakrishnan, B.; Jain, Y. K.

1983-08-01

A concept is developed which overcomes the defects of the nonlinearity of response and limitation in range exhibited by the V-slit, N-slit, and crossed slit sun sensors normally used for sun elevation angle measurements on spinning spacecraft. Two versions of sensors based on this concept which give a linear output and have a range of nearly + or - 90 deg of elevation angle are examined. Results are presented for the application of the twin slit version of the sun sensor in the three Indian satellites, Rohini, Apple, and Bhaskara II, which was successfully used for spin rate control and spin axis orientation control corrections as well as for sun elevation angle and spin period measurements.

Raman, FTIR, thermal and optical properties of TeO2-Nb2O5-B2O3-V2O5 quaternary glass system

Directory of Open Access Journals (Sweden)

Swapna

2017-07-01

Full Text Available A series of quaternary glass systems with the composition 79TeO2-(20−xNb2O5-xB2O3-1V2O5 was prepared using the melt quench technique. Such studies as optical absorption, Raman, FTIR spectroscopy, EPR and DSC were carried out on the glass system. The physical properties, such as density (ρ and molar volume (VM, were determined. The Urbach energy (ΔE, optical band gap (Eopt, optical basicity (Λ, refractive index (n and electron polarizability (α of the glasses were determined from optical absorption data. Spin-Hamiltonian parameters of VO2+ ions were calculated from the EPR data. With the gradual substitution of B2O3 at the expense of Nb2O5, the density and optical band gap of the glasses decreased, and the electronic polarizability increased. EPR spectra revealed that VO2+ occupies an octahedral site with tetrahedral compression. Spin-Hamiltonian parameters g|| and g⊥ increased as B2O3 content increased in the glass. The glass transition temperature (Tg also decreased as the B2O3 content in the glass increased.

Effects of coexisting spin disorder and antiferromagnetism on the magnetic behavior of nanostructured (Fe{sub 79}Mn{sub 21}){sub 1−x}Cu{sub x} alloys

Energy Technology Data Exchange (ETDEWEB)

Mizrahi, M., E-mail: mizrahi@fisica.unlp.edu.ar, E-mail: cabrera@fisica.unlp.edu.ar [INIFTA-CCT- La Plata-CONICET and Departamento de Física, Facultad de Ciencias Exactas, C. C. 67, Universidad Nacional de La Plata, 1900 La Plata (Argentina); Cabrera, A. F., E-mail: mizrahi@fisica.unlp.edu.ar, E-mail: cabrera@fisica.unlp.edu.ar; Desimoni, J. [IFLP-CCT-La Plata-CONICET and Departamento de Física, Facultad de Ciencias Exactas C.C. 67, Universidad Nacional de La Plata, 1900 La Plata (Argentina); Stewart, S. J. [IFLP-CCT-La Plata-CONICET and Departamento de Física, Facultad de Ciencias Exactas C.C. 67, Universidad Nacional de La Plata, 1900 La Plata (Argentina); Instituto Ciencias de la Salud, Universidad Nacional Arturo Jauretche, Av. Calchaquí No. 6200, Florencio Varela (Argentina)

2014-06-07

We report a magnetic study on nanostructured (Fe{sub 79}Mn{sub 21}){sub 1−x}Cu{sub x} (0.00 ≤ x ≤ 0.30) alloys using static magnetic measurements. The alloys are mainly composed by an antiferromagnetic fcc phase and a disordered region that displays a spin-glass-like behavior. The interplay between the antiferromagnetic and magnetically disordered phases establishes an exchange anisotropy that gives rise to a loop shift at temperatures below the freezing temperature of moments belonging to the disordered region. The loop shift is more noticeable as the Cu content increases, which also enhances the spin-glass-like features. Further, in the x = 0.30 alloy the alignment imposed by applied magnetic fields higher than 4 kOe prevail over the configuration determined by the frustration mechanism that characterizes the spin glass-like phase.

High-level waste borosilicate glass: A compendium of corrosion characteristics. Volume 3

International Nuclear Information System (INIS)

Cunnane, J.C.

1994-03-01

The objective of this document is to summarize scientific information pertinent to evaluating the extent to which high-level waste borosilicate glass corrosion and the associated radionuclide release processes are understood for the range of environmental conditions to which waste glass may be exposed in service. Alteration processes occurring within the bulk of the glass (e.g., devitrification and radiation-induced changes) are discussed insofar as they affect glass corrosion. Volume III contains a bibliography of glass corrosion studies, including studies that are not cited in Volumes I and II

High-level waste borosilicate glass: A compendium of corrosion characteristics. Volume 3

Energy Technology Data Exchange (ETDEWEB)

Cunnane, J.C. [comp.; Bates, J.K.; Bradley, C.R. [Argonne National Lab., IL (United States)] [and others

1994-03-01

The objective of this document is to summarize scientific information pertinent to evaluating the extent to which high-level waste borosilicate glass corrosion and the associated radionuclide release processes are understood for the range of environmental conditions to which waste glass may be exposed in service. Alteration processes occurring within the bulk of the glass (e.g., devitrification and radiation-induced changes) are discussed insofar as they affect glass corrosion. Volume III contains a bibliography of glass corrosion studies, including studies that are not cited in Volumes I and II.

Spectroscopic and optical properties of the VO2+ ion doped TeO2-TiO2-ZnO-Nb2O5 glass system

Science.gov (United States)

Swapna; Upender, G.; Sreenivasulu, V.; Prasad, M.

2016-04-01

Studies such as optical absorption, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Electron paramagnetic resonance (EPR) spectroscopy and Differential scanning calorimetry (DSC) were carried out on VO2+ ion doped TeO2-TiO2-ZnO-Nb2O5 glass system. Raman and FTIR spectra of the glasses revealed the presence of [TeO3], [TeO4] and [NbO6] structural units in the glass network. The Urbach energy (Δ E), cut-off wavelength (λ c ), optical band gap ( E opt ), optical basicity (Λ) and electron polarizability ( α) of the glasses were determined from optical absorption studies. The density ( ρ), molar volume ( V m ), oxygen molar volume ( V o ) and refractive index ( n) were also measured. Spin-Hamiltonian parameters were calculated from the EPR studies. When Nb2O5 was increased at the expense of ZnO, the density, optical band gap and Urbach energy of the glasses increased, and the electronic polarizability and optical basicity decreased. The EPR spectra clearly showed that vanadium was in the glass as VO2+ and occupied octahedral sites with tetrahedral compression. Spin-Hamiltonian parameters g‖ and g⊥ decreased as Nb2O5 content increased in the glass. The glass transition temperature ( T g ) also increased with increasing Nb2O5 content in the glass.

Radionuclides containment in nuclear glasses. An overview

Energy Technology Data Exchange (ETDEWEB)

Gin, Stephane; Jollivet, Patrick; Tribet, Magaly; Peuget, Sylvain; Schuller, Sophie [CEA Marcoule, Bagnols-sur-Ceze (France). DE2D SEVT

2017-07-01

Radioactive waste vitrification has been carried out industrially in several countries for nearly 40 years. Research into the formulation and long term behavior of high and intermediate level waste glasses, mainly borosilicate compositions, is still continuing in order to (i) safely condition new types of wastes and (ii) design and demonstrate the safety of the disposal of these long-lived waste forms in a deep geological repository. This article presents a summary of current knowledge on the formulation, irradiation resistance and the chemical durability of these conditioning materials, with a special focus on the fate of radionuclides during glass processing and aging. It is shown that, apart from the situation for certain elements with very low incorporation rate in glass matrices, vitrification in borosilicate glass can enable waste loadings of up to ∝20 wt% while maintaining the glass homogeneity for geological time scales and guaranteeing a high stability level in spite of irradiation and water contact.

Corrosion of synthesized glasses and glazes as analogs for nuclear waste glass degradation

International Nuclear Information System (INIS)

Vandiver, P.B.

1994-01-01

Synthesized glasses provide an opportunity to study natural corrosion processes which are intermediate in time span between geological examples of natural glasses, such as obsidians and tektites, and relatively short term laboratory tests lasting a few hours to several decades. In addition, synthesized glasses can usually be tracked to particular archaeological find sites with known dates of production and often burial. Environmental conditions are routinely measured at archaeological sites as a part of the excavation-process, such that information is available on the yearly cycling of temperature and relative humidity, sometimes at the depth at which the artifact was found. Whether the artifacts were excavated in an air enclosure, such as a tomb, or in the soil can also be reconstructed, such that one can determine whether aqueous or atmospheric corrosion was involved in the degradation process. For instance, so-called open-quotes Roman glassclose quotes may span a time period of production of 800 years and a geographical range from Germany to North Africa and from Britain to Afghanistan. One example is the storage during World War II of glass from the British Museum in underground metro stations. Some of these glasses have been in collections for over 100 years. Thus, populations of glasses can be chosen for experimentation which compare variations in bulk composition, dopants, microstructure, heat treatment, ground vs. fire polished surfaces, aqueous vs. atmospheric corrosion, geographic, geological as well as recent storage conditions. Glasses in museums are generally considered to have had their corrosion arrested and be stable because changes in visual appearance are not obvious. However, if we attempt to measure the range of surface water content in these glasses using Fourier transform infrared analysis, a considerable variability is found, as shown

Magnetic field dependence of static correlations and spin dynamics of reentrant spin glasses studied by neutron scattering

International Nuclear Information System (INIS)

Hennion, M.; Hennion, B.; Mirebeau, I.; Lequien, S.; Hippert, F.

1988-01-01

We report small angle (SANS) and inelastic neutron scattering in zero and applied field for a-FeMn, NiMn and AuFe at composition where both ferromagnetic and frustration characters occur. We discuss the field evolution of the transverse correlations which arise below T c . A study of the field sensitivity of the spin wave anomalies in a-FeMn is reported

Positron annihilation study of structural subnanovoids and irradiation damages in silica-based glasses

International Nuclear Information System (INIS)

Inoue, K.

2004-01-01

Structural subnanovoids in glass solidified with radioactive waste disposal were studied by positron annihilation 2-dimensional angular correlation and positron life time measurements. Positroniums in crystalline SiO 2 were in a delocalized state, but in glass SiO 2 were in a localized state. Pick-off annihilation (pair annihilation between an ortho-positroniums and a spin antiparallel electron) rate was shortened with decreasing molarity of glass network formers and consequently radii of structural subnanovoids were reduced. The sizes of structural subnanovoids determined from the pick-off annihilation were good agreement with those measured by momentum distribution of para-positroniums. In waste disposal model glass, no presence of positronims indicated that radioactive substances occupied almost all subnanovoids, and therefore voids with large size enough to localize positroniums (above 0.1 nm radius) could not be present. (Y. Kazumata)

Mn induced ferromagnetism spin fluctuation enhancement in Sr{sub 2}Ru{sub 1−x}Mn{sub x}O{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Zheng, Long; Cai, Jinzhu; Xie, Qiyun; Lv, Bin [Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Mao, Z.Q. [Department of Physics and Engineering Physics, Tulane University, New Orleans, LA 70118 (United States); Wu, X.S., E-mail: xswu@nju.edu.cn [Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China)

2013-09-15

We establish that Sr{sub 2}RuO{sub 4} is extremely close to incommensurate spin density wave instability. With increasing Mn content, the RuO{sub 6} octahedron in the unit cell varies. The octahedron of RuO{sub 6} contracts along c-axis for x<0.20, Mn element mainly showing the +3 chemical valence (Mn{sup 3+}), and it expands along c-axis with further increasing Mn content (x>0.20), and Mn element shows the +4 chemical valence (Mn{sup 4+}). Spin-glass-related ferromagnetism enhancement is observed for x>0.20, which indicates the critical ferromagnetic spin fluctuation due to Mn doping in Sr{sub 2}Ru{sub 1−x}Mn{sub x}O{sub 4}. - Highlights: • The chemical valence of Mn ions changed from Mn{sup 3+} to Mn{sup 4+} with the increase of Mn content. • Spin-glass-related ferromagnetism enhancement behavior is observed. • The electrical resistivity can be fitted using Mott's variable-range hopping model. • The evolution of octahedron with increase of Mn content is given. • The spin fluctuation effect plays an important role in the magnetic property.

Deuteron NMR (Nuclear Magnetic Resonance) in relation to the glass transition in polymers

Science.gov (United States)

Roessler, E.; Sillescu, H.; Spiess, H. W.; Wallwitz, R.

1983-01-01

H-2NMR is introduced as a tool for investigating slow molecular motion in the glass transition region of amorphous polymers. In particular, we compare H-2 spin alignment echo spectra of chain deuterated polystyrene with model calculations for restricted rotational Brownian motion. Molecular motion in the polyztyrene-toluene system has been investigated by analyzing H-2NMR of partially deuterated polystyrene and toluene, respectively. The diluent mobility in the mixed glass has been decomposed into solid and liquid components where the respective average correlation times differ by more than 5 decades.

An Economic Theory of the Glass Ceiling

OpenAIRE

Paul A. Grout; In-Uck Park; Silvia Sonderegger

2007-01-01

The glass ceiling is one of the most controversial and emotive aspects of employment in organisations. This paper provides a model of the glass ceiling that exhibits the following features that are frequently thought to characterise the problem: (i) there is a lower number of female employees in higher positions, (ii) women have to work harder than men to obtain equivalent jobs, (iii) women are then paid less than men when promoted, and (iv) some organisations are more female friendly than ot...

Antiferromagnetic coupling in a six-coordinate high spin cobalt(II)-semiquinonato complex.

Science.gov (United States)

Caneschi, Andrea; Dei, Andrea; Gatteschi, Dante; Tangoulis, Vassilis

2002-07-01

The 3,5-di-tert-butyl-catecholato and 9,10-phenanthrenecatecholato adducts of the cobalt-tetraazamacrocycle complex Co(Me(4)cyclam)(2+) (Me(4)cyclam = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) were synthesized and oxidized. The oxidation reaction products were isolated in the solid state as hexafluorophosphate derivatives. Both these complexes can be formulated as 1:1 cobalt(II)-semiquinonato complexes, that is, Co(Me(4)cyclam)(DBSQ)PF(6) (1) and Co(Me(4)cyclam)(PhSQ)PF(6) (2), in the temperature range 4-300 K, in striking contrast with the charge distribution found in similar adducts formed by related tetraazamacrocycles. The synthesis strategy and the structural, spectroscopic, and magnetic properties are reported and discussed. The crystallographic data for 2 are as follows: monoclinic, space group P2(1)/a, nomicron. 14, a = 14.087(4) A, b = 15.873(4) A, c = 14.263 (7) A, alpha = 89.91(3) degrees, beta = 107.34(2) degrees, gamma = 90.08(2) degrees, Z = 4. Both these complexes are characterized by triplet electronic ground states arising from the antiferromagnetic coupling between the high-spin d(7) metal ion and the radical ligand.

Spin-state studies with XES and RIXS: From static to ultrafast

International Nuclear Information System (INIS)

Vankó, György; Bordage, Amélie; Glatzel, Pieter; Gallo, Erik; Rovezzi, Mauro; Gawelda, Wojciech; Galler, Andreas; Bressler, Christian; Doumy, Gilles; March, Anne Marie; Kanter, Elliot P.; Young, Linda; Southworth, Stephen H.; Canton, Sophie E.; Uhlig, Jens; Smolentsev, Grigory; Sundström, Villy; Haldrup, Kristoffer; Brandt van Driel, Tim; Nielsen, Martin M.

2013-01-01

Highlights: ► We study light-induced spin-state transition of Fe(II) complexes in solution. ► Laser-pump-X-ray-probe spectroscopy is extended to MHz repetition rates. ► XES and RIXS compare well with the static spectra at thermal spin transition. ► The typical assumptions used in XES line shape analysis are validated. -- Abstract: We report on extending hard X-ray emission spectroscopy (XES) along with resonant inelastic X-ray scattering (RIXS) to study ultrafast phenomena in a pump-probe scheme at MHz repetition rates. The investigated systems include low-spin (LS) Fe II complex compounds, where optical pulses induce a spin-state transition to their (sub)nanosecond-lived high-spin (HS) state. Time-resolved XES clearly reflects the spin-state variations with very high signal-to-noise ratio, in agreement with HS–LS difference spectra measured at thermal spin crossover, and reference HS–LS systems in static experiments, next to multiplet calculations. The 1s2p RIXS, measured at the Fe 1s pre-edge region, shows variations after laser excitation, which are consistent with the formation of the HS state. Our results demonstrate that X-ray spectroscopy experiments with overall rather weak signals, such as RIXS, can now be reliably exploited to study chemical and physical transformations on ultrafast time scales

EVENT GENERATOR FOR RHIC SPIN PHYSICS

International Nuclear Information System (INIS)

SAITO, N.; SCHAEFER, A.

1999-01-01

This volume archives the reports from the RIKEN BNL Research Center workshop on ''Event Generator for RHIC Spin Physics II'' held during the week March 15, 1999 at Brookhaven National Laboratory. It was the second meeting on the subject following a first one in last September. This workshop has been initiated to establish a firm collaboration between theorists and experimentalists involved in RHIC spin physics with the aim of developing a reliable, high-precision event generator for RHIC spin physics. Needless to say, adequate event generators are indispensable tools for high energy physics programs in general, especially in the process of: planning the experimental programs; developing algorithms to extract the physics signals of interest; estimating the background in the extracted results, and connecting the final particle kinematics to the fundamental i.e. partonic level processes. Since RHIC is the first polarized collider, dedicated efforts are required to obtain a full-fledged event generator which describes spin dependent reactions in great detail

Structure, biodegradation behavior and cytotoxicity of alkali-containing alkaline-earth phosphosilicate glasses.

Science.gov (United States)

Kansal, Ishu; Reddy, AlluAmarnath; Muñoz, Francisco; Choi, Seong-Jun; Kim, Hae-Won; Tulyaganov, Dilshat U; Ferreira, José M F

2014-11-01

We report on the effect of sodium on the structure, chemical degradation and bioactivity of glasses in the CaO-MgO-SiO2-P2O5-CaF2 system. The (29)Si and (31)P magic angle spinning-nuclear magnetic resonance spectroscopy of melt-quenched glasses with varying Na2O/MgO ratios exhibit a silicate glass network with the dominance of Q(2)(Si) units and phosphorus mainly forming orthophosphate species. Sodium incorporation in the glasses did not induce a significant structural change in the silicate network, while it did influence the phosphate environment due to its lower ionic field strength in comparison with that of magnesium. The apatite forming ability of glasses has been investigated by immersion of glass powders in simulated body fluid (SBF) for time durations varying between 1h and 7 days while their chemical degradation has been studied in Tris-HCl in accordance with ISO-10993-14. Increasing Na(+)/Mg(2+) ratio caused a decrease in the chemical durability of glasses and in the apatite forming ability especially during initial steps of interaction between glass and SBF solution. The cellular responses were observed in vitro on bulk glass samples using mouse-derived pre-osteoblastic MC3T3-E1 cell line. The preliminary study suggested that the increasing alkali-concentration in glasses led to cytotoxicity in the cell culture medium. Copyright © 2014 Elsevier B.V. All rights reserved.

New instruments at IPNS: POSY II and SAD II

International Nuclear Information System (INIS)

Crawford, R.K.; Felcher, G.P.; Kleb, R.; Epperson, J.E.; Thiyagarajan, P.

1988-01-01

Three new instruments are currently in varying degrees of development/construction at IPNS. One of these, the Glass, Liquid, and Amorphous Materials Diffractometer (GLAD) is the subject of a separate paper in these Proceedings, and so will not be discussed further here. The other two, a second neutron reflectometer (POSY II) and a second small-angle diffractometer (SAD II) are described briefly below. 5 refs., 1 fig., 1 tab

Spin Physics at COMPASS

International Nuclear Information System (INIS)

Schill, Christian

2012-01-01

The COMPASS experiment is a fixed target experiment at the CERN SPS using muon and hadron beams for the investigation of the spin structure of the nucleon and hadron spectroscopy. The main objective of the muon physics program is the study of the spin of the nucleon in terms of its constituents, quarks and gluons. COMPASS has accumulated data during 6 years scattering polarized muons off longitudinally or transversely polarized deuteron ( 6 LiD) or proton (NH 3 ) targets. Results for the gluon polarization are obtained from longitudinal double spin cross section asymmetries using two different channels, open charm production and high transverse momentum hadron pairs, both proceeding through the photon-gluon fusion process. Also, the longitudinal spin structure functions of the proton and the deuteron were measured in parallel as well as the helicity distributions for the three lightest quark flavours. With a transversely polarized target, results were obtained with proton and deuteron targets for the Collins and Sivers asymmetries for charged hadrons as well as for identified kaons and pions. The Collins asymmetry is sensitive to the transverse spin structure of the nucleon, while the Sivers asymmetry reflects correlations between the quark transverse momentum and the nucleon spin. Recently, a new proposal for the COMPASS II experiment was accepted by the CERN SPS which includes two new topics: Exclusive reactions like DVCS and DVMP using the muon beam and a hydrogen target to study generalized parton distributions and Drell-Yan measurements using a pion beam and a polarized NH 3 target to study transverse momentum dependent distributions.

The order parameter of glass transition: Spontaneously delocalized nanoscale solitary wave with transverse ripplon-like soft wave

Directory of Open Access Journals (Sweden)

Jia Lin Wu

2013-06-01

Full Text Available In macromolecular self-avoiding random walk, movement of each chain-particle accompanies an instantaneous spin system with de Gennes n = 0 that provides extra energy, extra vacancy volume and relaxation time needed for chain-particles co-movement. Using these additional and instantaneous spin systems not only directly yields the same Brownian motion mode in glass transition (GT and reptation-tube model, but also proves that the entangled chain length corresponding to the Reynolds number in hydrodynamics and the inherent diffusion - delocalization mode of entangled chains, from frozen glass state to melt liquid state, is a chain-size solitary wave with transverse ripplon-like soft wave. Thus, the order parameter of GT is found. The various currently available GT theories, such as Static Replica, Random First-Order Transition, Potential Energy Landscape, Mode-Coupling and Nanoscale Heterogeneity, can be unified using the additional and instantaneous spin system. GT served as an inspiration and continues to serve as the paradigm in the universal random delocalization transitions from disorder to more disorder until turbulence.

Charge density glass dynamics - Soft potentials and soft modes

Energy Technology Data Exchange (ETDEWEB)

Biljakovic, K., E-mail: katica@ifs.hr [Institute of Physics, HR-10001, Zagreb, P.O. Box 304 (Croatia); Staresinic, D., E-mail: damirs@ifs.hr [Institute of Physics, HR-10001, Zagreb, P.O. Box 304 (Croatia); Lasjaunias, J.C., E-mail: jean-claude.lasjaunias@pop3.grenoble.cnrs.fr [Institut Neel, CNRS, BP 166, F-38042, Grenoble, Cedex 9 (France); Remenyi, G., E-mail: Gyorgy.Remenyi@grenoble.cnrs.fr [Institut Neel, CNRS, BP 166, F-38042, Grenoble, Cedex 9 (France); Melin, R., E-mail: Regis.Melin@grenoble.cnrs.fr [Institut Neel, CNRS, BP 166, F-38042, Grenoble, Cedex 9 (France); Monceau, P., E-mail: pierre.monceau@grenoble.cnrs.fr [Institut Neel, CNRS, BP 166, F-38042, Grenoble, Cedex 9 (France); Sahling, S., E-mail: sven.olaf@gmail.com [Institut fuer Festkoerperphysik, Universitaet Dresden, D-01062, Dresden (Germany)

2012-06-01

An universal fingerprint of glasses has been found in low-temperature thermodynamic properties of charge/spin density wave (C/SDW) systems. Deviations from the well-known Debye, elastic continuum prediction for specific heat (flat C{sub p}/T{sup 3} plot) appear as two anomalies; the upturn below 1 K and a broad bump at T{approx}10 K (named Boson peak in glasses). The first one, inherent of localized two level systems within the shalow corrugated phase space, exhibits slow relaxation with the complex dynamics. The second one, 'Boson peak-like peak' was attributed to the pinned mode and incomplete softening of CDW superstructural mode. We discuss similar C{sub p}(T) features found also in incommensurate dielectrics with well documented soft-mode anomalies.

Configurational entropy of polar glass formers and the effect of electric field on glass transition

Energy Technology Data Exchange (ETDEWEB)

Matyushov, Dmitry V., E-mail: dmitrym@asu.edu [Department of Physics and School of Molecular Sciences, Arizona State University, P.O. Box 871504, Tempe, Arizona 85287 (United States)

2016-07-21

A model of low-temperature polar liquids is constructed that accounts for the configurational heat capacity, entropy, and the effect of a strong electric field on the glass transition. The model is based on the Padé-truncated perturbation expansions of the liquid state theory. Depending on parameters, it accommodates an ideal glass transition of vanishing configurational entropy and its avoidance, with a square-root divergent enumeration function at the point of its termination. A composite density-temperature parameter ρ{sup γ}/T, often used to represent combined pressure and temperature data, follows from the model. The theory is in good agreement with the experimental data for excess (over the crystal state) thermodynamics of molecular glass formers. We suggest that the Kauzmann entropy crisis might be a signature of vanishing configurational entropy of a subset of degrees of freedom, multipolar rotations in our model. This scenario has observable consequences: (i) a dynamical crossover of the relaxation time and (ii) the fragility index defined by the ratio of the excess heat capacity and excess entropy at the glass transition. The Kauzmann temperature of vanishing configurational entropy and the corresponding glass transition temperature shift upward when the electric field is applied. The temperature shift scales quadratically with the field strength.

Configurational entropy of polar glass formers and the effect of electric field on glass transition.

Science.gov (United States)

Matyushov, Dmitry V

2016-07-21

A model of low-temperature polar liquids is constructed that accounts for the configurational heat capacity, entropy, and the effect of a strong electric field on the glass transition. The model is based on the Padé-truncated perturbation expansions of the liquid state theory. Depending on parameters, it accommodates an ideal glass transition of vanishing configurational entropy and its avoidance, with a square-root divergent enumeration function at the point of its termination. A composite density-temperature parameter ρ(γ)/T, often used to represent combined pressure and temperature data, follows from the model. The theory is in good agreement with the experimental data for excess (over the crystal state) thermodynamics of molecular glass formers. We suggest that the Kauzmann entropy crisis might be a signature of vanishing configurational entropy of a subset of degrees of freedom, multipolar rotations in our model. This scenario has observable consequences: (i) a dynamical crossover of the relaxation time and (ii) the fragility index defined by the ratio of the excess heat capacity and excess entropy at the glass transition. The Kauzmann temperature of vanishing configurational entropy and the corresponding glass transition temperature shift upward when the electric field is applied. The temperature shift scales quadratically with the field strength.

/sup 13/C-/sup 13/C spin-spin coupling constants in structural investigations. II. Conformational structure of vinyl ethers

Energy Technology Data Exchange (ETDEWEB)

Krivdin, L.B.; Shcherbakov, V.V.; Bzhezovskii, V.M.; Kalabin, G.A.

1986-10-10

The /sup 13/C-/sup 13/C spin-spin coupling constants between the carbon nuclei of the vinyl group were measured for a series of vinyl ethers. It was established that the unshared electron pairs of the oxygen atom can make a substantial stereospecific contribution to the direct /sup 13/C-/sup 13/C constants of the adjacent nuclei. The observed effect was used to establish the conformational structure of the compounds.

Low-temperature Synthesis of Tin(II) Oxide From Tin(II) ketoacidoximate Precursor

KAUST Repository

Alshankiti, Buthainah

2015-04-01

Sn (II) oxide finds numerous applications in different fields such as thin film transistors1, solar cells2 and sensors.3 In this study we present the fabrication of tin monoxide SnO by using Sn (II) ketoacid oximate complexes as precursors. Tin (II) ketoacidoximates of the type [HON=CRCOO]2Sn where R= Me 1, R= CH2Ph 2, and [(MeON=CMeCOO)3Sn]- NH4 +.2H2O 3 were synthesized by in situ formation of the ketoacid oximate ligand. The crystal structures were determined via single crystal X- ray diffraction of the complexes 1-3 revealed square planar and square pyramidal coordination environments for the Sn atom. Intramolecular hydrogen bonding is observed in all the complexes. Furthermore, the complexes were characterized by Infrared (IR), Nuclear Magnetic Resonance (NMR) and elemental analysis. From thermogravimetric analysis of 1-3, it was found that the complexes decomposed in the range of 160 – 165 oC. Analysis of the gases evolved during decomposition indicated complete loss of the oximato ligand in one step and the formation of SnO. Spin coating of 1 on silicon or glass substrate show uniform coating of SnO. Band gaps of SnO films were measured and found to be in the range of 3.0 – 3.3 eV by UV-Vis spectroscopy. X-ray photoelectron spectroscopy indicated surface oxidation of the SnO film. Heating 1 above 140 oC in air gives SnO of size ranging from 10 – 500 nm and is spherical in shape. The SnO nanomaterial is characterized by powder X-ray diffraction(XRD), Raman spectroscopy, Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM).

The electronic and optical properties of germanium tellurite glasses containing various transition metal oxides

International Nuclear Information System (INIS)

Khan, M.N.

1988-01-01

Various transition metal oxides, such as TiO 2 , V 2 O 5 , NiO, CuO, and ZnO are added to germanium-tellurite glass and measurements are reported of the electrical conductivity, density, optical absorption, infra-red absorption spectra, and electron spin resonance. It is found that the d.c. conductivity of glasses containing the same amount of V 2 O 5 is higher than that of germanium tellurite glasses containing a similar amount of other transition metal oxides, and is due to hopping between localized states. The optical absorption measurements show that the fundamental absorption edge is a function of glass composition and the optical absorption is due to forbidden indirect transitions. From the infra-red absorption spectra, it is found that the addition of transition metal oxides does not introduce any new absorption band in the infra-red spectrum of germanium tellurite glasses. A small shift of existing absorptions toward higher wave number is observed. The ESR measurements revealed that some transition metal ions are diamagnetic while others are paramagnetic in the glass network. (author)

Reduction-oxidation Enabled Glass-ceramics to Stainless Steel Bonding Part II interfacial bonding analysis

Energy Technology Data Exchange (ETDEWEB)

Dai, Steve Xunhu [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2015-09-01

Among glass-ceramic compositions modified with a variety of oxidants (AgO, FeO, NiO, PbO, SnO, CuO, CoO, MoO₃ and WO₃) only CuO and CoO doped glass-ceramics showed existence of bonding oxides through reduction-oxidation (redox) at the GC-SS interface. The CuO-modified glass-ceramics demonstrate the formation of a continuous layer of strong bonding Cr₂O₃ at the interface in low partial oxygen (PO₂) atmosphere. However, in a local reducing atmosphere, the CuO is preferentially reduced at the surface of glass-ceramic rather than the GC-SS interface for redox. The CoO-modified glass-ceramics demonstrate improved GC-SS bonding. But the low mobility of Co⁺⁺ ions in the GC limited the amount of CoO that can diffuse to and participate in redox at the interface.

Numerical simulation of spin-qubit operation in coupled quantum dots

International Nuclear Information System (INIS)

Goto, Daisuke; Eto, Mikio

2007-01-01

Electronic states and spin operation in coupled quantum dots are numerically studied, considering realistic shape of quantum dots and electron-electron interaction. (i) We evaluate the spin coupling J between two electron spins, as a function of magnetic field perpendicular to the quantum dots. We observe a transition from antiferromagnetic coupling (J>0) to ferromagnetic coupling (J<0) at magnetic field of a few Tesla. The spin coupling is hardly influenced by the size difference between the quantum dots if the energy levels are matched. (ii) We simulate SWAP gate operations by calculating the time development of two electron spins. We show that a sudden change of tunnel barrier may result in the gate errors. The spin exchange is incomplete in the presence of strong spin-orbit interaction in InGaAs. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Spin effects in strong-field laser-electron interactions

International Nuclear Information System (INIS)

Ahrens, S; Bauke, H; Müller, T-O; Villalba-Chávez, S; Müller, C

2013-01-01

The electron spin degree of freedom can play a significant role in relativistic scattering processes involving intense laser fields. In this contribution we discuss the influence of the electron spin on (i) Kapitza-Dirac scattering in an x-ray laser field of high intensity, (ii) photo-induced electron-positron pair production in a strong laser wave and (iii) multiphoton electron-positron pair production on an atomic nucleus. We show that in all cases under consideration the electron spin can have a characteristic impact on the process properties and their total probabilities. To this end, spin-resolved calculations based on the Dirac equation in the presence of an intense laser field are performed. The predictions from Dirac theory are also compared with the corresponding results from the Klein-Gordon equation.

Voltage-controlled spin selection in a magnetic resonant tunneling diode.

Science.gov (United States)

Slobodskyy, A; Gould, C; Slobodskyy, T; Becker, C R; Schmidt, G; Molenkamp, L W

2003-06-20

We have fabricated all II-VI semiconductor resonant tunneling diodes based on the (Zn,Mn,Be)Se material system, containing dilute magnetic material in the quantum well, and studied their current-voltage characteristics. When subjected to an external magnetic field the resulting spin splitting of the levels in the quantum well leads to a splitting of the transmission resonance into two separate peaks. This is interpreted as evidence of tunneling transport through spin polarized levels, and could be the first step towards a voltage controlled spin filter.

The role of halides on a chromium ligand field in lead borate glasses

Science.gov (United States)

Sekhar, K. Chandra; Srinivas, B.; Narsimlu, N.; Narasimha Chary, M.; Shareefuddin, Md

2017-10-01

Glasses with a composition of PbX-PbO-B2O3 (X  =  F2, Cl2 and Br2) containing Cr3+ ions were prepared by a melt quenching technique and investigated by using x-ray diffraction (XRD), optical absorption and electron paramagnetic resonance (EPR) studies. X-ray diffractograms revealed the amorphous nature of the glasses. The density and molar volume were determined. Density values increased for the PFPBCR glass system and decreased for the PCPBCR and PBPBCR glass systems with the composition. Optical absorption spectra were recorded at room temperature (RT) to evaluate the optical band gap E opt and Urbach energies. All the spectra showed characteristic peaks at around 450 nm, 600 nm and 690 nm, and they are assigned to 4 A 2g  →  4 T 1g, 4 A 2g  →  4 T 2g, 4 A 2g  →  2 E transitions respectively. From the optical absorption spectral data, the crystal field (D q ) and Racah parameters (B and C) have been evaluated. Variations in optical band gaps were explained using the electro negativity of halide ions. Electron paramagnetic resonance (EPR) studies were carried out by introducing Cr3+ as the spin probe. The EPR spectra of all the glass samples were recorded at X-band frequencies. The EPR spectra exhibit two resonance signals with effective g values at g  ≈  4.82 and g  ≈  1.99 and are attributed to isolated Cr3+ ions and exchange coupled Cr3+ pairs respectively. The number of spins along with susceptibility are also calculated from the EPR spectra.

Polypyridyl iron(II) complexes showing remarkable photocytotoxicity ...

Indian Academy of Sciences (India)

reported a high spin (S=5/2) ternary iron(III) complex. [Fe(BHA)(L)Cl] of a ... designed low-spin iron(II) complexes as a new class of ..... They were moderately soluble in methanol, ethanol and .... Cell permeable DCFDA on oxidation by cel-.

Spin Propensities of Octahedral Complexes From Density Functional Theory

DEFF Research Database (Denmark)

Mortensen, Sara R.; Kepp, Kasper Planeta

2015-01-01

assessment of spin state propensities versus ligand and metal type and reveal, e.g., that CN- is consistently weaker than CO for M(II) but stronger than CO for M(III) and SCN- and NCS- change order in M(II) versus M(III) complexes. Contrary to expectation based on the spectrochemical series, Cl- and Br...

Spin diffusion in the Mn2+ ion system of II-VI diluted magnetic semiconductor heterostructures

Science.gov (United States)

Maksimov, A. A.; Yakovlev, D. R.; Debus, J.; Tartakovskii, I. I.; Waag, A.; Karczewski, G.; Wojtowicz, T.; Kossut, J.; Bayer, M.

2010-07-01

The magnetization dynamics in diluted magnetic semiconductor heterostructures based on (Zn,Mn)Se and (Cd,Mn)Te were studied optically and simulated numerically. In samples with inhomogeneous magnetic ion distribution, these dynamics are contributed by spin-lattice relaxation and spin diffusion in the Mn spin system. A spin-diffusion coefficient of 7×10-8cm2/s was evaluated for Zn0.99Mn0.01Se from comparison of experiment and theory. Calculations of the exciton giant Zeeman splitting and the magnetization dynamics in ordered alloys and digitally grown parabolic quantum wells show perfect agreement with the experimental data. In both structure types, spin diffusion contributes essentially to the magnetization dynamics.

Dynamics and thermodynamics of polymer glasses.

Science.gov (United States)

Cangialosi, D

2014-04-16

The fate of matter when decreasing the temperature at constant pressure is that of passing from gas to liquid and, subsequently, from liquid to crystal. However, a class of materials can exist in an amorphous phase below the melting temperature. On cooling such materials, a glass is formed; that is, a material with the rigidity of a solid but exhibiting no long-range order. The study of the thermodynamics and dynamics of glass-forming systems is the subject of continuous research. Within the wide variety of glass formers, an important sub-class is represented by glass forming polymers. The presence of chain connectivity and, in some cases, conformational disorder are unfavourable factors from the point of view of crystallization. Furthermore, many of them, such as amorphous thermoplastics, thermosets and rubbers, are widely employed in many applications. In this review, the peculiarities of the thermodynamics and dynamics of glass-forming polymers are discussed, with particular emphasis on those topics currently the subject of debate. In particular, the following aspects will be reviewed in the present work: (i) the connection between the pronounced slowing down of glassy dynamics on cooling towards the glass transition temperature (Tg) and the thermodynamics; and, (ii) the fate of the dynamics and thermodynamics below Tg. Both aspects are reviewed in light of the possible presence of a singularity at a finite temperature with diverging relaxation time and zero configurational entropy. In this context, the specificity of glass-forming polymers is emphasized.

Mean-field solution of the Potts glass near the transition temperature to the ordered phase

Czech Academy of Sciences Publication Activity Database

Janiš, Václav; Klíč, Antonín

2011-01-01

Roč. 84, č. 6 (2011), "064446-1"-"064446-10" ISSN 1098-0121 Institutional research plan: CEZ:AV0Z10100520 Keywords : Potts glass * hierarchic solutions with replicated spins * continuous replica-symmetry breaking Subject RIV: BE - Theoretical Physics Impact factor: 3.691, year: 2011

Entangled spins and ghost-spins

Directory of Open Access Journals (Sweden)

Dileep P. Jatkar

2017-09-01

Full Text Available 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 [20] 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 ghost-spins. With an odd number of ghost-spins however, we find that there always exist positive norm states with negative real part for entanglement entropy after tracing over the ghost-spins.

Surface modification of glass beads with glutaraldehyde: Characterization and their adsorption property for metal ions

Energy Technology Data Exchange (ETDEWEB)

Ozmen, Mustafa; Can, Keziban; Akin, Ilker; Arslan, Gulsin [Department of Chemistry, Selcuk University, 42031, Konya (Turkey); Tor, Ali, E-mail: ali.alitor@gmail.com [Department of Environmental Engineering, Selcuk University, Engineering Faculty, Campus, 42031, Konya (Turkey); Cengeloglu, Yunus; Ersoz, Mustafa [Department of Chemistry, Selcuk University, 42031, Konya (Turkey)

2009-11-15

In this study, a new material that adsorbs the metal ions was prepared by modification of the glass beads surfaces with glutaraldehyde. First, the glass beads were etched with 4 M NaOH solution. Then, they were reacted with 3-aminopropyl-triethoxysilane (APTES). Finally, silanized glass beads were treated with 25% of glutaraldehyde solution. The characterization studies by using Fourier Transform Infrared Spectroscopy (FT-IR), Thermal Gravimetric Analysis (TGA), elemental analysis and Scanning Electron Microscopy (SEM) indicated that modification of the glass bead surfaces was successfully performed. The adsorption studies exhibited that the modified glass beads could be efficiently used for the removal of the metal cations and anion (chromate ion) from aqueous solutions via chelation and ion-exchange mechanisms. For both Pb(II) and Cr(VI), selected as model ions, the adsorption equilibrium was achieved in 60 min and adsorption of both ions followed the second-order kinetic model. It was found that the sorption data was better represented by the Freundlich isotherm in comparison to the Langmuir and Redlich-Peterson isotherm models. The maximum adsorption capacities for Pb(II) and Cr(VI) were 9.947 and 11.571 mg/g, respectively. The regeneration studies also showed that modified glass beads could be re-used for the adsorption of Pb(II) and Cr(VI) from aqueous solutions over three cycles.

Spin Current Noise of the Spin Seebeck Effect and Spin Pumping

Science.gov (United States)

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

2018-01-01

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

Magnetic ordering of CoCl2-GIC, a spin ceramic: hierarchical successive transitions and the intermediate glassy phase

International Nuclear Information System (INIS)

Suzuki, Masatsugu; Suzuki, Itsuko S; Matsuura, Motohiro

2007-01-01

Stage-2 CoCl 2 -graphite intercalation compound (GIC) is a spin ceramic which shows hierarchical successive transitions at T cu (= 8.9 K) and T cl (= 7.0 K) from the paramagnetic phase into an intra-cluster (two-dimensional ferromagnetic) order with inter-cluster disorder and then to an inter-cluster (three-dimensional antiferromagnetic like) order over the whole system. The nature of the inter-cluster disorder was suggested to be of spin glass by nonlinear magnetic response analyses around T cu and by studies on dynamical aspects of ordering between T cu and T cl . Here, we present a further extensive examination of a series of time dependence of zero-field cooled magnetization M ZFC after the ageing protocol below T cu . The time dependence of the relaxation rates S ZFC (t) = (1/H) dM ZFC (t)/dlnt dramatically changes from the curves of simple spin glass ageing effect below T cl to those of two peaks above T cl . The characteristic relaxation behaviour apparently indicates that there coexist two different kinds of glassy correlated region below T cu

Spin-Dependent Processes Measured without a Permanent Magnet.

Science.gov (United States)

Fontanesi, Claudio; Capua, Eyal; Paltiel, Yossi; Waldeck, David H; Naaman, Ron

2018-05-07

A novel Hall circuit design that can be incorporated into a working electrode, which is used to probe spin-selective charge transfer and charge displacement processes, is reviewed herein. The general design of a Hall circuit based on a semiconductor heterostructure, which forms a shallow 2D electron gas and is used as an electrode, is described. Three different types of spin-selective processes have been studied with this device in the past: i) photoinduced charge exchange between quantum dots and the working electrode through chiral molecules is associated with spin polarization that creates a local magnetization and generates a Hall voltage; ii) charge polarization of chiral molecules by an applied voltage is accompanied by a spin polarization that generates a Hall voltage; and iii) cyclic voltammetry (current-voltage) measurements of electrochemical redox reactions that can be spin-analyzed by the Hall circuit to provide a third dimension (spin) in addition to the well-known current and voltage dimensions. The three studies reviewed open new doors into understanding both the spin current and the charge current in electronic materials and electrochemical processes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermal conductivity of Glycerol's liquid, glass, and crystal states, glass-liquid-glass transition, and crystallization at high pressures.

Science.gov (United States)

Andersson, Ove; Johari, G P

2016-02-14

To investigate the effects of local density fluctuations on phonon propagation in a hydrogen bonded structure, we studied the thermal conductivity κ of the crystal, liquid, and glassy states of pure glycerol as a function of the temperature, T, and the pressure, p. We find that the following: (i) κcrystal is 3.6-times the κliquid value at 140 K at 0.1 MPa and 2.2-times at 290 K, and it varies with T according to 138 × T(-0.95); (ii) the ratio κliquid (p)/κliquid (0.1 MPa) is 1.45 GPa(-1) at 280 K, which, unexpectedly, is about the same as κcrystal (p)/κcrystal (0.1 MPa) of 1.42 GPa(-1) at 298 K; (iii) κglass is relatively insensitive to T but sensitive to the applied p (1.38 GPa(-1) at 150 K); (iv) κglass-T plots show an enhanced, pressure-dependent peak-like feature, which is due to the glass to liquid transition on heating; (v) continuous heating cold-crystallizes ultraviscous glycerol under pressure, at a higher T when p is high; and (vi) glycerol formed by cooling at a high p and then measured at a low p has a significantly higher κ than the glass formed by cooling at a low p. On heating at a fixed low p, its κ decreases before its glass-liquid transition range at that p is reached. We attribute this effect to thermally assisted loss of the configurational and vibrational instabilities of a glass formed at high p and recovered at low p, which is different from the usual glass-aging effect. While the heat capacity, entropy, and volume of glycerol crystal are less than those for its glass and liquid, κcrystal of glycerol, like its elastic modulus and refractive index, is higher. We discuss these findings in terms of the role of fluctuations in local density and structure, and the relations between κ and the thermodynamic quantities.

1D and 2D assembly structures by imidazole···chloride hydrogen bonds of iron(II) complexes [Fe(II)(HL(n-Pr))3]Cl·Y (HL(n-Pr) = 2-methylimidazol-4-yl-methylideneamino-n-propyl; Y = AsF6, BF4) and their spin states.

Science.gov (United States)

Fujinami, Takeshi; Nishi, Koshiro; Matsumoto, Naohide; Iijima, Seiichiro; Halcrow, Malcolm A; Sunatsuki, Yukinari; Kojima, Masaaki

2011-12-07

Two Fe(II) complexes fac-[Fe(II)(HL(n-Pr))(3)]Cl·Y (Y = AsF(6) (1) and BF(4) (2)) were synthesized, where HL(n-Pr) is 2-methylimidazole-4-yl-methylideneamino-n-propyl. Each complex-cation has the same octahedral N(6) geometry coordinated by three bidentate ligands and assumes facial-isomerism, fac-[Fe(II)(HL(n-Pr))(3)](2+) with Δ- and Λ-enantiomorphs. Three imidazole groups per Δ- or Λ-fac-[Fe(II)(HL(n-Pr))(3)](2+) are hydrogen-bonded to three Cl(-) ions or, from the viewpoint of the Cl(-) ion, one Cl(-) ion is hydrogen-bonded to three neighbouring fac-[Fe(II)(HL(n-Pr))(3)](2+) cations. The 3 : 3 NH···Cl(-) hydrogen bonds between Δ- or Λ-fac-[Fe(II)(HL(n-Pr))(3)](2+) and Cl(-) generate two kinds of assembly structures. The directions of the 3 : 3 NH···Cl(-) hydrogen bonds and hence the resulting assembly structures are determined by the size of the anion Y, though Y is not involved into the network structure and just accommodated in the cavity. Compound 1 has a 1D ladder structure giving a larger cavity, in which the Δ- and Λ-fac-[Fe(II)(HL(n-Pr))(3)](2+) enantiomorphs are bridged by two NH···Cl(-) hydrogen bonds. Compound 2 has a 2D network structure with a net unit of a cyclic trimer of {fac-[Fe(II)(HL(n-Pr))(3)](2+)···Cl(-)}(3) giving a smaller cavity, in which Δ- or Λ-fac-[Fe(II)(HL(n-Pr))(3)](2+) species with the same chirality are linked by NH···Cl(-) hydrogen bonds to give a homochiral 2D network structure. Magnetic susceptibility and Mössbauer spectral measurements demonstrated that compound 1 showed an abrupt one-step spin crossover with 4.0 K thermal hysteresis of T(c↓) = 125.5 K and T(c↑) = 129.5 K and compound 2 showed no spin transition and stayed in the high-spin state over the 5-300 K temperature range.

Glass-embedded two-dimensional silicon photonic crystal devices with a broad bandwidth waveguide and a high quality nanocavity.

Science.gov (United States)

Jeon, Seung-Woo; Han, Jin-Kyu; Song, Bong-Shik; Noda, Susumu

2010-08-30

To enhance the mechanical stability of a two-dimensional photonic crystal slab structure and maintain its excellent performance, we designed a glass-embedded silicon photonic crystal device consisting of a broad bandwidth waveguide and a nanocavity with a high quality (Q) factor, and then fabricated the structure using spin-on glass (SOG). Furthermore, we showed that the refractive index of the SOG could be tuned from 1.37 to 1.57 by varying the curing temperature of the SOG. Finally, we demonstrated a glass-embedded heterostructured cavity with an ultrahigh Q factor of 160,000 by adjusting the refractive index of the SOG.

QuSpin: a Python package for dynamics and exact diagonalisation of quantum many body systems part I: spin chains

Directory of Open Access Journals (Sweden)

Phillip Weinberg, Marin Bukov

2017-02-01

Full Text Available We present a new open-source Python package for exact diagonalization and quantum dynamics of spin(-photon chains, called QuSpin, supporting the use of various symmetries in 1-dimension and (imaginary time evolution for chains up to 32 sites in length. The package is well-suited to study, among others, quantum quenches at finite and infinite times, the Eigenstate Thermalisation hypothesis, many-body localisation and other dynamical phase transitions, periodically-driven (Floquet systems, adiabatic and counter-diabatic ramps, and spin-photon interactions. Moreover, QuSpin's user-friendly interface can easily be used in combination with other Python packages which makes it amenable to a high-level customisation. We explain how to use QuSpin using four detailed examples: (i Standard exact diagonalisation of XXZ chain (ii adiabatic ramping of parameters in the many-body localised XXZ model, (iii heating in the periodically-driven transverse-field Ising model in a parallel field, and (iv quantised light-atom interactions: recovering the periodically-driven atom in the semi-classical limit of a static Hamiltonian.

The correlation between fragility, density, and atomic interaction in glass-forming liquids

Energy Technology Data Exchange (ETDEWEB)

Wang, Lijin; Guan, Pengfei, E-mail: pguan@csrc.ac.cn [Beijing Computational Science Research Center, Beijing 100193 (China); Wang, W. H. [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

2016-07-21

The fragility that controls the temperature-dependent viscous properties of liquids as the glass transition is approached, in various glass-forming liquids with different softness of the repulsive part of atomic interactions at different densities, is investigated by molecular dynamic simulations. We show that the landscape of fragility in purely repulsive systems can be separated into three regions denoted as R{sub I,} R{sub II}, and R{sub III}, respectively, with qualitatively disparate dynamic behaviors: R{sub I} which can be described by “softness makes strong glasses,” R{sub II} where fragility is independent of softness and can only be tuned by density, and R{sub III} with constant fragility, suggesting that density plays an unexpected role for understanding the repulsive softness dependence of fragility. What is more important is that we unify the long-standing inconsistence with respect to the repulsive softness dependence of fragility by observing that a glass former can be tuned more fragile if nonperturbative attraction is added into it. Moreover, we find that the vastly dissimilar influences of attractive interaction on fragility could be estimated from the structural properties of related zero-temperature glasses.

The correlation between fragility, density, and atomic interaction in glass-forming liquids

International Nuclear Information System (INIS)

Wang, Lijin; Guan, Pengfei; Wang, W. H.

2016-01-01

The fragility that controls the temperature-dependent viscous properties of liquids as the glass transition is approached, in various glass-forming liquids with different softness of the repulsive part of atomic interactions at different densities, is investigated by molecular dynamic simulations. We show that the landscape of fragility in purely repulsive systems can be separated into three regions denoted as R I, R II , and R III , respectively, with qualitatively disparate dynamic behaviors: R I which can be described by “softness makes strong glasses,” R II where fragility is independent of softness and can only be tuned by density, and R III with constant fragility, suggesting that density plays an unexpected role for understanding the repulsive softness dependence of fragility. What is more important is that we unify the long-standing inconsistence with respect to the repulsive softness dependence of fragility by observing that a glass former can be tuned more fragile if nonperturbative attraction is added into it. Moreover, we find that the vastly dissimilar influences of attractive interaction on fragility could be estimated from the structural properties of related zero-temperature glasses.

Angular dependence and symmetry of Rashba spin torque in ferromagnetic heterostructures

KAUST Repository

Ortiz Pauyac, Christian

2013-06-26

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

Angular dependence and symmetry of Rashba spin torque in ferromagnetic heterostructures

KAUST Repository

Ortiz Pauyac, Christian; Wang, Xuhui; Chshiev, Mairbek; Manchon, Aurelien

2013-01-01

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

Short chain lead (II) alkanoates as ionic liquids and glass formers: A d.s.c., X-ray diffraction and FTIR spectroscopy study

International Nuclear Information System (INIS)

Martinez Casado, F.J.; Sanchez Arenas, A.; Garcia Perez, M.V.; Redondo Yelamos, M.I.; Lopez de Andres, S.; Cheda, J.A.R.

2007-01-01

Three members of the lead (II) n-alkanoates (from etanoate to n-butanoate) have been synthesized, purified and studied by d.s.c., X-ray diffraction, and FTIR spectroscopy. Lead (II) acetate, propanoate, and butanoate present only a melting transition at T = (452.6, 398.2, and 346.5) K, with Δ f H = (16.0, 13.1, and 15.6) kJ . mol -1 , and Δ f S (35.3, 32.8, and 45.1) J . mol -1 . K -1 , respectively. These temperature data correct to a great extent the historical values reported in the literature. These three members readily quench into a glass state. Their corresponding T g values are (314.4, 289.0, and 274.9) K, respectively, measured by d.s.c. at a heating rate of 5 K . min -1