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Sample records for spin changing transitions

  1. Sudden transition and sudden change from open spin environments

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Zheng-Da [Zhejiang Institute of Modern Physics and Physics Department, Zhejiang University, Hangzhou 310027 (China); School of Science, Jiangnan University, Wuxi 214122 (China); Xu, Jing-Bo, E-mail: xujb@zju.edu.cn [Zhejiang Institute of Modern Physics and Physics Department, Zhejiang University, Hangzhou 310027 (China); Yao, Dao-Xin [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996 (United States)

    2014-11-15

    We investigate the necessary conditions for the existence of sudden transition or sudden change phenomenon for appropriate initial states under dephasing. As illustrative examples, we study the behaviors of quantum correlation dynamics of two noninteracting qubits in independent and common open spin environments, respectively. For the independent environments case, we find that the quantum correlation dynamics is closely related to the Loschmidt echo and the dynamics exhibits a sudden transition from classical to quantum correlation decay. It is also shown that the sudden change phenomenon may occur for the common environment case and stationary quantum discord is found at the high temperature region of the environment. Finally, we investigate the quantum criticality of the open spin environment by exploring the probability distribution of the Loschmidt echo and the scaling transformation behavior of quantum discord, respectively. - Highlights: • Sudden transition or sudden change from open spin baths are studied. • Quantum discord is related to the Loschmidt echo in independent open spin baths. • Steady quantum discord is found in a common open spin bath. • The probability distribution of the Loschmidt echo is analyzed. • The scaling transformation behavior of quantum discord is displayed.

  2. Does the solid-liquid crystal phase transition provoke the spin-state change in spin-crossover metallomesogens?

    Science.gov (United States)

    Seredyuk, M; Gaspar, A B; Ksenofontov, V; Galyametdinov, Y; Kusz, J; Gütlich, P

    2008-01-30

    Three types of interplay/synergy between spin-crossover (SCO) and liquid crystalline (LC) phase transitions can be predicted: (i) systems with coupled phase transitions, where the structural changes associated to the CrLC phase transition drives the spin-state transition, (ii) systems where both transitions coexist in the same temperature region but are not coupled, and (iii) systems with uncoupled phase transitions. Here we present a new family of Fe(II) metallomesogens based on the ligand tris[3-aza-4-((5-C(n))(6-R)(2-pyridyl))but-3-enyl]amine, with C(n) = hexyloxy, dodecyloxy, hexadecyloxy, octadecyloxy, eicosyloxy, R = hydrogen or methyl (C(n)-trenH or C(n)-trenMe), which affords examples of systems of types i, ii, and iii. Self-assembly of the ligands C(n)-trenH and C(n)-trenMe with Fe(A)2 x xH2O salts have afforded a family of complexes with general formula [Fe(C(n)-trenR)](A)2 x sH2O (s > or = 0), with A = ClO4(-), F-, Cl-, Br- and I-. Single-crystal X-ray diffraction measurements have been performed on two derivatives of this family, named as [Fe(C6-trenH)](ClO4)2 (C(6)-1) and [Fe(C6-trenMe)](ClO4)2 (C(6)-2), at 150 K for C(6)-1 and at 90 and 298 K for C(6)-2. At 150 K, C(6)-1 displays the triclinic space group P, whereas at 90 and at 298 K C(6)-2 adopts the monoclinic P2(1)/c space group. In both compounds the iron atoms adopt a pseudo-octahedral symmetry and are surrounded by six nitrogen atoms belonging to imino groups and pyridines of the ligands C(n)-trenH and C(n)-trenMe. The average Fe(II)-N bonds (1.963(2) A) at 150 K denote that C(6)-1 is in the low-spin (LS) state. For C(6)-2 the average Fe(II)-N bonds (2.007(1) A) at 90 K are characteristic of the LS state, while at 298 K they are typical for the high-spin (HS) state (2.234(3) A). Compound C(6)-1 and [Fe(C18-trenH)](ClO4)2 (C(18)-1) adopts the LS state in the temperature region between 10 and 400 K, while compound C(6)-2 and [Fe(Cn-trenMe)](ClO4)2 (n = 12 (C(12)-2), 18 (C(18)-2)) exhibit spin

  3. Electronic Structure and Spin Configuration Trends of Single Transition Metal Impurity in Phase Change Material

    Science.gov (United States)

    Li, H.; Pei, J.; Shi, L. P.

    2016-10-01

    Fe doped phase change material GexSbyTez has shown experimentally the ability to alter its magnetic properties by phase change. This engineered spin degree of freedom into the phase change material offers the possibility of logic devices or spintronic devices where they may enable fast manipulation of ferromagnetism by a phase change mechanism. The electronic structures and spin configurations of isolated transition metal dopant in phase change material (iTM-PCM) is important to understand the interaction between localized metal d states and the unique delocalized host states of phase change material. Identifying an impurity center that has, in isolation, a nonvanishing magnetic moment is the first step to study the collective magnetic ordering, which originates from the interaction among close enough individual impurities. Theoretical description of iTM-PCM is challenging. In this work, we use a screened exchange hybrid functional to study the single 3d transition metal impurity in crystalline GeTe and GeSb2Te4. By curing the problem of local density functional (LDA) such as over-delocalization of the 3d states, we find that Fe on the Ge/Sb site has its majority d states fully occupied while its minority d states are empty, which is different from the previously predicted electronic configuration by LDA. From early transition metal Cr to heavier Ni, the majority 3d states are gradually populated until fully occupied and then the minority 3d states begin to be filled. Interpretive orbital interaction pictures are presented for understanding the local and total magnetic moments.

  4. Does the Spin Transition in Mantle Silicate Perovskite Change the Seismic Properties of the Lower Mantle? (Invited)

    Science.gov (United States)

    Shim, S.; Grocholski, B.; Catalli, K.; Sturhahn, W.; Prakapenka, V.

    2010-12-01

    Recent studies have shown that iron in perovskite and ferropericlase undergoes a spin transition at mantle-related pressures, but it has been unclear if the spin transition can change the seismic properties of the lower mantle. One of the difficulties in experimental studies has been the complex crystal chemistry of perovskite, i.e., Fe2+, Fe3+, and Al in two different cation sites. We have conducted X-ray diffraction and spectroscopy in the laser-heated diamond-anvil cell under quasi-hydrostatic conditions and controlled redox state to measure the properties of perovskite in six different compositions: pure MgSiO3 and MgSiO3 with Fe2+ only (Lundin et al., 2008; Grocholski et al., 2009), Fe3+ only (Catalli et al., 2010), Al only, Fe3+ and Al, and Fe2+, Fe3+, and Al. Because the different compositions were measured using the same experimental setup, our dataset provides an accurate measure of the effects of composition on density (dlnρ/dX) and bulk sound speed (dlnVΦ/dX) through comparison within an internally consistent dataset. Fe2+ remains high spin at least up to 70 GPa and does not change the equation of state of perovskite. Therefore, dlnρ/dX(Fe2+) and dlnVΦ/dX(Fe2+) remain nearly constant throughout the lower mantle. Fe3+ undergoes a gradual spin transition between 0 and 55 GPa in Al-free perovskite and a sharp spin transition at 70 GPa in aluminous perovskite. The spin transition of Fe3+ results in a change in the bulk modulus of perovskite. In aluminous perovskite, Fe3+ induces a volume collapse, similar to ferropericlase, resulting in an increase in density at ~1800 km depth. The spin transition of Fe3+ unlikely results in a seismic discontinuity in the lower mantle, due to its gradual nature and thermal effects. However, Fe3+ makes dlnVΦ more negative by a factor of 3 compared with Fe2+ before its spin transition and makes dlnVΦ comparable to Fe2+ or even positive after the spin transition. Therefore, Fe3+-rich heterogeneities (e.g., basalt) may

  5. In Situ AFM Imaging of Microstructural Changes Associated with The Spin Transition in [Fe(Htrz)₂(Trz)](Bf₄) Nanoparticles.

    Science.gov (United States)

    Manrique-Juárez, María D; Suleimanov, Iurii; Hernández, Edna M; Salmon, Lionel; Molnár, Gábor; Bousseksou, Azzedine

    2016-06-30

    Topographic images of [Fe(Htrz)₂(trz)](BF₄) nanoparticles were acquired across the first-order spin transition using variable-temperature atomic force microscopy (AFM) in amplitude modulation mode. These studies revealed a complex morphology of the particles consisting of aggregates of small nanocrystals, which expand, separate and re-aggregate due to the mechanical stress during the spin-state switching events. Both reversible (prompt or slow recovery) and irreversible effects (fatigue) on the particle morphology were evidenced and correlated with the spin crossover properties.

  6. Spin-Liquid-to-Spin-Liquid Transition in Kitaev Magnets Driven by Fractionalization.

    Science.gov (United States)

    Nasu, Joji; Kato, Yasuyuki; Yoshitake, Junki; Kamiya, Yoshitomo; Motome, Yukitoshi

    2017-03-31

    While phase transitions between magnetic analogs of the three states of matter-a long-range ordered state, paramagnet, and spin liquid-are extensively studied, the possibility of "liquid-liquid" transitions, namely, between different spin liquids, remains elusive. By introducing the additional Ising coupling into the honeycomb Kitaev model with bond asymmetry, we discover that the Kitaev spin liquid turns into a spin-nematic quantum paramagnet before a magnetic order is established by the Ising coupling. The quantum phase transition between the two liquid states accompanies a topological change driven by fractionalized excitations, the Z_{2} gauge fluxes, and is of first order. At finite temperatures, this yields a persisting first-order transition line that terminates at a critical point located deep inside the regime where quantum spins are fractionalized. It is suggested that similar transitions may occur in other perturbed Kitaev magnets with bond asymmetry.

  7. Surface transition in spin crossover nanoparticles

    Science.gov (United States)

    Mikolasek, Mirko; Nicolazzi, William; Terki, Férial; Molnár, Gábor; Bousseksou, Azzedine

    2017-06-01

    The spin transition in a square lattice nanoparticle, whose the primitive cell is constituted of 2 metallic centres, is investigated using a two-variable elastic Ising-like model solved by Monte Carlo simulations. We show that the specific lattice geometry can lead to an important surface relaxation of both the structure and the spin-state, which are analysed by mapping the local strain. The consequence of this surface relaxation is the occurrence of a stepwise spin transition where the surface and the core switch at different temperatures.

  8. Spin-Orbitronics at Transition Metal Interfaces

    KAUST Repository

    Manchon, Aurelien

    2017-11-09

    The presence of large spin–orbit interaction at transition metal interfaces enables the emergence of a variety of fascinating phenomena that have been at the forefront of spintronics research in the past 10 years. The objective of the present chapter is to offer a review of these various effects from a theoretical perspective, with a particular focus on spin transport, chiral magnetism, and their interplay. After a brief description of the orbital hybridization scheme at transition metal interfaces, we address the impact of spin–orbit coupling on the interfacial magnetic configuration, through the celebrated Dzyaloshinskii–Moriya interaction. We then discuss the physics of spin transport and subsequent torques occurring at these interfaces. We particularly address the spin Hall, spin swapping, and inverse spin-galvanic effects. Finally, the interplay between flowing charges and chiral magnetic textures and their induced dynamics are presented. We conclude this chapter by proposing some perspectives on promising research directions.

  9. Spin doping using transition metal phthalocyanine molecules

    Science.gov (United States)

    Atxabal, A.; Ribeiro, M.; Parui, S.; Urreta, L.; Sagasta, E.; Sun, X.; Llopis, R.; Casanova, F.; Hueso, L. E.

    2016-12-01

    Molecular spins have become key enablers for exploring magnetic interactions, quantum information processes and many-body effects in metals. Metal-organic molecules, in particular, let the spin state of the core metal ion to be modified according to its organic environment, allowing localized magnetic moments to emerge as functional entities with radically different properties from its simple atomic counterparts. Here, using and preserving the integrity of transition metal phthalocyanine high-spin complexes, we demonstrate the magnetic doping of gold thin films, effectively creating a new ground state. We demonstrate it by electrical transport measurements that are sensitive to the scattering of itinerant electrons with magnetic impurities, such as Kondo effect and weak antilocalization. Our work expands in a simple and powerful way the classes of materials that can be used as magnetic dopants, opening a new channel to couple the wide range of molecular properties with spin phenomena at a functional scale.

  10. Direct Evidence of the Symmetry Change of Co-3d Orbitals Associated with the Spin-State Transition in LaCoO3 by X-ray Compton Scattering

    Science.gov (United States)

    Kobayashi, Yoshihiko; Sakurai, Yoshiharu; Itou, Masayoshi; Sato, Keisuke; Asai, Kichizo

    2015-11-01

    We have investigated the electron momentum density of Co-3d electrons in LaCoO3 using X-ray Compton scattering in order to demonstrate the symmetry change of the Co(3d) electron orbital states through the spin-state transition. The electron momentum density reconstructed from the Compton profiles indicates the symmetry change in the 3d electron-orbital states between below and above 100 K, which provides the first microscopic direct evidence for the orbital symmetry change of occupied electronic state associated with the spin-state transition in LaCoO3. The reproduced electron orbital states show a covalent bond with O-2p orbitals, which is responsible for the collectiveness in the characteristics of the spin-state transition.

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

    Science.gov (United States)

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

    2016-01-01

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

  12. In Situ AFM Imaging of Microstructural Changes Associated with The Spin Transition in [Fe(Htrz)2(Trz)](Bf4) Nanoparticles

    Science.gov (United States)

    Manrique-Juárez, María D.; Suleimanov, Iurii; Hernández, Edna M.; Salmon, Lionel; Molnár, Gábor; Bousseksou, Azzedine

    2016-01-01

    Topographic images of [Fe(Htrz)2(trz)](BF4) nanoparticles were acquired across the first-order spin transition using variable-temperature atomic force microscopy (AFM) in amplitude modulation mode. These studies revealed a complex morphology of the particles consisting of aggregates of small nanocrystals, which expand, separate and re-aggregate due to the mechanical stress during the spin-state switching events. Both reversible (prompt or slow recovery) and irreversible effects (fatigue) on the particle morphology were evidenced and correlated with the spin crossover properties. PMID:28773659

  13. In Situ AFM Imaging of Microstructural Changes Associated with The Spin Transition in [Fe(Htrz2(Trz](Bf4 Nanoparticles

    Directory of Open Access Journals (Sweden)

    María D. Manrique-Juárez

    2016-06-01

    Full Text Available Topographic images of [Fe(Htrz2(trz](BF4 nanoparticles were acquired across the first-order spin transition using variable-temperature atomic force microscopy (AFM in amplitude modulation mode. These studies revealed a complex morphology of the particles consisting of aggregates of small nanocrystals, which expand, separate and re-aggregate due to the mechanical stress during the spin-state switching events. Both reversible (prompt or slow recovery and irreversible effects (fatigue on the particle morphology were evidenced and correlated with the spin crossover properties.

  14. Spin Transition Molecular Materials: New Sensors

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Y., E-mail: garcia@chim.ucl.ac.be; Ksenofontov, V.; Guetlich, P. [Universitaet Mainz, Institut fuer Anorganische Chemie und Analytische Chemie (Germany)

    2002-03-15

    This short review article concerns a new family of iron(II) spin transition chain compounds containing 4-R-1,2,4-triazole derivatives whose properties have been followed by several physical techniques. A clear evidence of the LIESST effect at 20 K has been found for one of these materials by {sup 57}Fe Moessbauer spectroscopy. Potential applications in terms of pressure and thermal sensors are discussed.

  15. Sudden transition from finite temperature spin environments

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Zheng-Da; He, Qi-Liang; Xu, Hang-Shi [Zhejiang Institute of Modern Physics and Physics Department, Zhejiang University, Hangzhou 310027 (China); Xu, Jing-Bo, E-mail: xujb@zju.edu.cn [Zhejiang Institute of Modern Physics and Physics Department, Zhejiang University, Hangzhou 310027 (China)

    2012-10-01

    We investigate the phenomenon of sudden transition from finite temperature critical environments in the study of quantum correlations of a two-qubit system coupled to independent thermal Ising baths. The influence of the temperature and external field of bath on the critical time of sudden transition is also explored. It is found that the phenomenon of sudden transition can be used to detect the critical points of thermal spin environments. How to protect quantum correlations of the system is also examined by applying a series of π-phase pulses. -- Highlights: ► The sudden transition phenomenon from thermal critical environments is studied. ► How to detect quantum critical points of thermal Ising baths is explored. ► The quantum discord can be protected against thermal bath by π-phase pulses.

  16. Spin transition in Fe3+ in Mg-silicate perovskite

    Science.gov (United States)

    Catalli, K.; Shim, S.; Prakapenka, V. B.; Zhao, J.; Sturhahn, W.; Liu, H.

    2008-12-01

    In recent years, spin transitions have been reported in both perovskite (Pv) (Badro et al., 2004) and magnesiowüstite (Mw) (Lin et al., 2005). Although no density change has been detected in ferrous iron bearing Pv (Lundin et al., 2008), large changes in density have been found to occur with the spin transition in Mw (Fei et al., 2007). This difference has been attributed to the diverse coordination and oxidation states of Fe in Pv and has made analysis of previous experimental data difficult. We have measured synchrotron Mössbauer spectroscopy (SMS) and X-ray diffraction (XRD) on Mg-silicate Pv with all Fe in Fe3+ (0.9MgSiO3- 0.1Fe2O3) up to 136 GPa in the laser heated diamond anvil cell with an argon pressure medium. Our SMS shows that Fe3+ enters both the dodecahedral and octahedral sites at the entire pressure range we studied (47-136 GPa). We found that both high and low spin Fe3+ exist in the octahedral site between 47 and 63 GPa and then all Fe3+ in the octahedral site becomes low spin at higher pressures, while Fe3+ in the dodecahedral site remains high spin to 136 GPa. Pressure-volume data, measured up to 106 GPa using the gold pressure scale (Tsuchiya, 2003), shows that the spin transition does not effect density but does result in a 10% increase in the bulk modulus near 60 GPa. Below 60 GPa, ferric Pv is 9% more compressible than ferrous Pv, but above 60 GPa, ferric Pv is 17% less compressible than ferrous perovskite. This change in compressibility is likely due to a change in compression mechanism: at low pressure compression is accomplished by a combination of the gradual spin collapse and lattice compression. However, after the spin transition is complete, only lattice compression is at work at higher pressures. If the lower mantle has as much Fe3+ as suggested by McCammon et al. (1997) and Frost et al. (2004), this may result in a global discontinuity at the mid-mantle. If not, local enrichment of Fe3+ can result in a discontinuity, which can be

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

    National Research Council Canada - National Science Library

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

    2016-01-01

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

  18. Analysis of multi-step transitions in spin crossover nanochains

    Energy Technology Data Exchange (ETDEWEB)

    Chiruta, Daniel [GEMaC, Université de Versailles Saint-Quentin-en-Yvelines, CNRS-UVSQ (UMR 8635), 78035 Versailles Cedex (France); LISV, Université de Versailles Saint-Quentin-en-Yvelines, 78140 Velizy (France); Faculty of Electrical Engineering and Computer Science, Stefan cel Mare University, Suceava 720229 (Romania); Linares, Jorge, E-mail: jorge.linares@uvsq.fr [GEMaC, Université de Versailles Saint-Quentin-en-Yvelines, CNRS-UVSQ (UMR 8635), 78035 Versailles Cedex (France); Garcia, Yann, E-mail: yann.garcia@uclouvain.be [Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain, Molecules, Solids and Reactivity (IMCN/MOST), Place Louis Pasteur, 1, 1348 Louvain-la-Neuve (Belgium); Dimian, Mihai [Faculty of Electrical Engineering and Computer Science, Stefan cel Mare University, Suceava 720229 (Romania); Dahoo, Pierre Richard [LATMOS, Université de Versailles-Saint-Quentin-en-Yvelines, CNRS-UPMC-UVSQ (UMR 8190), 78280 Guyancourt (France)

    2014-02-01

    The temperature driven phase transition occurring in spin crossover nanochains has been studied by an Ising-like model considering both short-range and long-range interactions. Various types of spin crossover profiles have been described in this framework, including a novel three-step transition identified in a nanosystem with eight molecules, which is modeled for the first time. A special interest has been also given to stepwise transitions accompanied by two hysteresis loops. The edge and size effects on spin crossover behavior have been investigated in order to get a deeper insight of the underlying mechanisms involved in these unusual spin transitions.

  19. Antiferromagnetic phase transition and spin correlations in NiO

    DEFF Research Database (Denmark)

    Chatterji, Tapan; McIntyre, G.J.; Lindgård, Per-Anker

    2009-01-01

    We have investigated the antiferromagnetic (AF) phase transition and spin correlations in NiO by high-temperature neutron diffraction below and above TN. We show that AF phase transition is a continuous second-order transition within our experimental resolution. The spin correlations manifested...... by the strong diffuse magnetic scattering persist well above TN530 K and could still be observed at T=800 K which is about 1.5TN. We argue that the strong spin correlations above TN are due to the topological frustration of the spins on a fcc lattice. The Néel temperature is substantially reduced...

  20. Phase transitions and thermal entanglement of the distorted Ising-Heisenberg spin chain: topology of multiple-spin exchange interactions in spin ladders.

    Science.gov (United States)

    Arian Zad, Hamid; Ananikian, Nerses

    2017-11-15

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

  1. Phase transitions and thermal entanglement of the distorted Ising–Heisenberg spin chain: topology of multiple-spin exchange interactions in spin ladders

    Science.gov (United States)

    Arian Zad, Hamid; Ananikian, Nerses

    2017-11-01

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

  2. Transition from spin accumulation into interface states to spin injection in silicon and germanium conduction bands

    Science.gov (United States)

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

    2013-04-01

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

  3. Photoinduced Coherent Spin Fluctuation in Primary Dynamics of Insulator to Metal Transition in Perovskite Cobalt Oxide

    Directory of Open Access Journals (Sweden)

    Arima T.

    2013-03-01

    Full Text Available Coherent spin fluctuation was detected in the photoinduced Mott insulator-metal transition in perovskite cobalt oxide by using 3 optical-cycle infrared pulse. Such coherent spin fluctuation is driven by the perovskite distortion changing orbital gap.

  4. The Verwey transition observed by spin-resolved photoemission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Figuera, Juan de la, E-mail: juan.delafiguera@iqfr.csic.es [Instituto de Química Física “Rocasolano”, CSIC, Madrid E-28006 (Spain); Tusche, Christian [Max Planck Institute of Microstructure Physics, Halle D-06120 (Germany); Forschungszentrum Jülich GmbH, Peter Grünberg Institut (PGI-6), D-52425 Jülich (Germany)

    2017-01-01

    Highlights: • First observations of magnetic domains on magnetite (001) by spin-resolved PEEM. • Spin-polarization through the Verwey transitions does not change appreciably. • Shape and distribution of domains has been observed through the Verwey transition. - Abstract: We have imaged the magnetic domains on magnetite (001) through the Verwey transition by means of spin-resolved photoemission electron microscopy. A He laboratory source is used for illumination. The magnetic domains walls above the Verwey transition are aligned with 〈110〉 in-plane directions. Below the Verwey transition, the domain structure is interpreted as arising from a distribution of areas with different monoclinic c-axis, with linear 180° domain walls within each area and ragged edges when the magnetic domain boundaries coincide with structural domain walls. The domains evolve above the Verwey transition, while they are static below.

  5. Giant spin-orbit-induced spin splitting in two-dimensional transition-metal dichalcogenide semiconductors

    KAUST Repository

    Zhu, Zhiyong

    2011-10-14

    Fully relativistic first-principles calculations based on density functional theory are performed to study the spin-orbit-induced spin splitting in monolayer systems of the transition-metal dichalcogenides MoS2, MoSe2, WS2, and WSe2. All these systems are identified as direct-band-gap semiconductors. Giant spin splittings of 148–456 meV result from missing inversion symmetry. Full out-of-plane spin polarization is due to the two-dimensional nature of the electron motion and the potential gradient asymmetry. By suppression of the Dyakonov-Perel spin relaxation, spin lifetimes are expected to be very long. Because of the giant spin splittings, the studied materials have great potential in spintronics applications.

  6. Spin-Orbital Order Modified by Orbital Dilution in Transition-Metal Oxides: From Spin Defects to Frustrated Spins Polarizing Host Orbitals

    Directory of Open Access Journals (Sweden)

    Wojciech Brzezicki

    2015-03-01

    Full Text Available We investigate the changes in spin and orbital patterns induced by magnetic transition-metal ions without an orbital degree of freedom doped in a strongly correlated insulator with spin-orbital order. In this context, we study the 3d ion substitution in 4d transition-metal oxides in the case of 3d^{3} doping at either 3d^{2} or 4d^{4} sites, which realizes orbital dilution in a Mott insulator. Although we concentrate on this doping case as it is known experimentally and more challenging than other oxides due to finite spin-orbit coupling, the conclusions are more general. We derive the effective 3d−4d (or 3d−3d superexchange in a Mott insulator with different ionic valencies, underlining the emerging structure of the spin-orbital coupling between the impurity and the host sites, and demonstrate that it is qualitatively different from that encountered in the host itself. This derivation shows that the interaction between the host and the impurity depends in a crucial way on the type of doubly occupied t_{2g} orbital. One finds that in some cases, due to the quench of the orbital degree of freedom at the 3d impurity, the spin and orbital order within the host is drastically modified by doping. The impurity either acts as a spin defect accompanied by an orbital vacancy in the spin-orbital structure when the host-impurity coupling is weak or favors doubly occupied active orbitals (orbital polarons along the 3d−4d bond leading to antiferromagnetic or ferromagnetic spin coupling. This competition between different magnetic couplings leads to quite different ground states. In particular, for the case of a finite and periodic 3d atom substitution, it leads to striped patterns either with alternating ferromagnetic or antiferromagnetic domains or with islands of saturated ferromagnetic order. We find that magnetic frustration and spin degeneracy can be lifted by the quantum orbital flips of the host, but they are robust in special regions of the

  7. Quantum phase transitions in spin-lattice systems

    CERN Document Server

    Ristig, M; Farnell, D; Kuerten, K

    2002-01-01

    Classical and quantized spins on a lattice interacting via unisotropic Heisenberg forces are important and illuminating models for an understanding of magnetic properties and phase transitions in solids, of structural phase transitions in ferroelectrics, and of transitions in quasi-spin systems. Further, many-body theories of spin lattices may be fruitfully related to latticized quantum-field theories within a Hamiltonian formulation. A close formal relationship exists, for example, between an O(2) model of the XY type and the O(4) model of chiral meson-field theory. Microscopic calculations are reviewed on the ground and excited states of such systems employing the microscopic correlated basis-functions (CBF) theory that has been so successful in the theory of quantum fluids and in nuclear physics. Reported are numerical results on the order parameters, phase boundaries, and other physical quantities of interest for the transverse Ising model, the spin-half XY model, the O(2) model for Josephson junction arr...

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

    Energy Technology Data Exchange (ETDEWEB)

    Chen, C.-C.

    2010-04-29

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

  9. Control of entanglement transitions in quantum spin clusters

    Science.gov (United States)

    Irons, Hannah R.; Quintanilla, Jorge; Perring, Toby G.; Amico, Luigi; Aeppli, Gabriel

    2017-12-01

    Quantum spin clusters provide a platform for the experimental study of many-body entanglement. Here we address a simple model of a single-molecule nanomagnet featuring N interacting spins in a transverse field. The field can control an entanglement transition (ET). We calculate the magnetization, low-energy gap, and neutron-scattering cross section and find that the ET has distinct signatures, detectable at temperatures as high as 5% of the interaction strength. The signatures are stronger for smaller clusters.

  10. Spin transition in arrays of gold nanoparticles and spin crossover molecules.

    Science.gov (United States)

    Devid, Edwin J; Martinho, Paulo N; Kamalakar, M Venkata; Šalitroš, Ivan; Prendergast, Úna; Dayen, Jean-François; Meded, Velimir; Lemma, Tibebe; González-Prieto, Rodrigo; Evers, Ferdinand; Keyes, Tia E; Ruben, Mario; Doudin, Bernard; van der Molen, Sense Jan

    2015-04-28

    We investigate if the functionality of spin crossover molecules is preserved when they are assembled into an interfacial device structure. Specifically, we prepare and investigate gold nanoparticle arrays, into which room-temperature spin crossover molecules are introduced, more precisely, [Fe(AcS-BPP)2](ClO4)2, where AcS-BPP = (S)-(4-{[2,6-(dipyrazol-1-yl)pyrid-4-yl]ethynyl}phenyl)ethanethioate (in short, Fe(S-BPP)2). We combine three complementary experiments to characterize the molecule-nanoparticle structure in detail. Temperature-dependent Raman measurements provide direct evidence for a (partial) spin transition in the Fe(S-BPP)2-based arrays. This transition is qualitatively confirmed by magnetization measurements. Finally, charge transport measurements on the Fe(S-BPP)2-gold nanoparticle devices reveal a minimum in device resistance versus temperature, R(T), curves around 260-290 K. This is in contrast to similar networks containing passive molecules only that show monotonically decreasing R(T) characteristics. Backed by density functional theory calculations on single molecular conductance values for both spin states, we propose to relate the resistance minimum in R(T) to a spin transition under the hypothesis that (1) the molecular resistance of the high spin state is larger than that of the low spin state and (2) transport in the array is governed by a percolation model.

  11. Role of entropy and structural parameters in the spin-state transition of LaCoO3

    Science.gov (United States)

    Chakrabarti, Bismayan; Birol, Turan; Haule, Kristjan

    2017-11-01

    The spin-state transition in LaCoO3 has eluded description for decades despite concerted theoretical and experimental effort. In this study, we approach this problem using fully charge self-consistent density functional theory + embedded dynamical mean field theory (DFT+DMFT). We show from first principles that LaCoO3 cannot be described by a single, pure spin state at any temperature. Instead, we observe a gradual change in the population of higher-spin multiplets with increasing temperature, with the high-spin multiplets being excited at the onset of the spin-state transition followed by the intermediate-spin multiplets being excited at the metal-insulator-transition temperature. We explicitly elucidate the critical role of lattice expansion and oxygen octahedral rotations in the spin-state transition. We also reproduce, from first principles, that the spin-state transition and the metal-insulator transition in LaCoO3 occur at different temperature scales. In addition, our results shed light on the importance of electronic entropy in driving the spin-state transition, which has so far been ignored in all first-principles studies of this material.

  12. Identifying a correlated spin fluctuation in an entangled spin chain subject to a quantum phase transition.

    Science.gov (United States)

    Shimizu, Kaoru; Tokura, Yasuhiro

    2015-12-01

    This paper presents a theoretical framework for analyzing the quantum fluctuation properties of a quantum spin chain subject to a quantum phase transition. We can quantify the fluctuation properties by examining the correlation between the fluctuations of two neighboring spins subject to the quantum uncertainty. To do this, we first compute the reduced density matrix ρ of the spin pair from the ground state |Ψ⟩ of a spin chain, and then identify the quantum correlation part ρ(q) embedded in ρ. If the spin chain is translationally symmetric and characterized by a nearest-neighbor two-body spin interaction, we can determine uniquely the form of ρ(q) as W|Φ〉〈Φ| with the weight W ≤1, and quantify the fluctuation properties using the two-spin entangled state |Φ〉. We demonstrate the framework for a transverse-field quantum Ising spin chain and indicate its validity for more general spin chain models.

  13. Field induced quantum phase transition in the anisotropic spin ladder

    Energy Technology Data Exchange (ETDEWEB)

    Rezania, Hamed, E-mail: rezania.hamed@gmail.com [Department of Physics, Razi University, Kermanshah (Iran, Islamic Republic of); Jesri, Sounya [Department of Physics, Razi University, Kermanshah (Iran, Islamic Republic of)

    2013-02-15

    We have studied the quantum phase transition between antiferromagnetic and spin liquid phases for field induced quasi-one dimensional spin ladder model Hamiltonian. Using bond operator formalism, the original spin Hamiltonian is mapped to bosonic one. Green's function approach has been implemented to get the low energy spectrum and the corresponding structure factor. The critical field (B{sub c}) for a fixed coupling exchange between two rungs is found based on the Bose-Einstein condensation of quasi-particles (triplons) which takes place when the spin excitation spectrum vanishes at the antiferromagnetic wave vector. We have investigated the effect of both intersite ({delta}) and local ({Delta}) anisotropy on the critical field, critical coupling exchange and transverse static structure factor of the field induced quasi-one dimensional antiferromagnetic anisotropic spin ladder model at zero temperature. We have also studied the divergent behavior of static spin structure factor when magnetic field approaches the critical point. - Highlights: Black-Right-Pointing-Pointer The calculation of quantum critical field of spin ladder Hamiltonian by Green's function approach. Black-Right-Pointing-Pointer The study of behavior of energy gap of spin excitation spectrum versus field and anisotropies. Black-Right-Pointing-Pointer The investigation of behavior of transverse structure factor in terms of magnetic field.

  14. Fingerprints of spin-orbital entanglement in transition metal oxides.

    Science.gov (United States)

    Oleś, Andrzej M

    2012-08-08

    The concept of spin-orbital entanglement on superexchange bonds in transition metal oxides is introduced and explained on several examples. It is shown that spin-orbital entanglement in superexchange models destabilizes the long-range (spin and orbital) order and may lead either to a disordered spin-liquid state or to novel phases at low temperature which arise from strongly frustrated interactions. Such novel ground states cannot be described within the conventionally used mean field theory which separates spin and orbital degrees of freedom. Even in cases where the ground states are disentangled, spin-orbital entanglement occurs in excited states and may become crucial for a correct description of physical properties at finite temperature. As an important example of this behaviour we present spin-orbital entanglement in the RV O(3) perovskites, with R = La,Pr,…,Y b,Lu, where the finite temperature properties of these compounds can be understood only using entangled states: (i) the thermal evolution of the optical spectral weights, (ii) the dependence of the transition temperatures for the onset of orbital and magnetic order on the ionic radius in the phase diagram of the RV O(3) perovskites, and (iii) the dimerization observed in the magnon spectra for the C-type antiferromagnetic phase of Y V O(3). Finally, it is shown that joint spin-orbital excitations in an ordered phase with coexisting antiferromagnetic and alternating orbital order introduce topological constraints for the hole propagation and will thus radically modify the transport properties in doped Mott insulators where hole motion implies simultaneous spin and orbital excitations.

  15. A spin transition molecular material with a wide bistability domain.

    Science.gov (United States)

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

    2002-11-04

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

  16. Topological Phase Transitions in the Photonic Spin Hall Effect

    Science.gov (United States)

    Kort-Kamp, W. J. M.

    2017-10-01

    The recent synthesis of two-dimensional staggered materials opens up burgeoning opportunities to study optical spin-orbit interactions in semiconducting Dirac-like systems. We unveil topological phase transitions in the photonic spin Hall effect in the graphene family materials. It is shown that an external static electric field and a high frequency circularly polarized laser allow for active on-demand manipulation of electromagnetic beam shifts. The spin Hall effect of light presents a rich dependence with radiation degrees of freedom, and material properties, and features nontrivial topological properties. We discover that photonic Hall shifts are sensitive to spin and valley properties of the charge carriers, providing an unprecedented pathway to investigate spintronics and valleytronics in staggered 2D semiconductors.

  17. Role of Entropy and Structural Parameters in the Spin State Transition of LaCoO3

    Science.gov (United States)

    Chakrabarti, Bismayan; Birol, Turan; Haule, Kristjan

    The spin state transition in LaCoO3 has eluded description for decades despite concerted theoretical and experimental effort. In this study, we approach this problem using fully charge consistent Density Functional Theory + Dynamical Mean Field Theory (DFT+DMFT). We show, from first principles, that LaCoO3 cannot be described by a single, pure spin state at any temperature, but instead shows a gradual change in the population of higher spin multiples as temperature is increased. We explicitly elucidate the critical role of the lattice expansion and oxygen octahedral rotations in the spin state transition. We also show that the spin state transition and the metal-insulator transition in the compound occur at different temperatures. In addition, our results shed light on the importance of electronic entropy, which has so far been ignored in all first principles studies of this material.

  18. Geometric structure, electronic structure, and spin transition of several Fe{sup II} spin-crossover molecules

    Energy Technology Data Exchange (ETDEWEB)

    Tuan, Nguyen Anh [Faculty of Physics, Hanoi University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi (Viet Nam)

    2012-04-01

    We present a density functional study on the geometric structure, electronic structure, and spin transition of a series of Fe{sup II} spin-crossover (SCO) molecules, i.e., [Fe(abpt){sub 2}(NCS){sub 2}] (1), [Fe(abpt){sub 2}(NCSe){sub 2}] (2), and [Fe(dpbo)(HIm){sub 2}] (3) with dpbo diethyl(E,E)-2,2'-[1,2-phenylbis(iminomethylidyne)]bis[3-oxobutanoate](2-), N',O{sup 3},O{sup 3}', and abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole in order to explore more about the way to control SCO behavior of transition metal complexes. Our calculated results show that the spin transition of these Fe{sup II} molecules is accompanied with charge transfer between the Fe atom and ligands. This causes change in the electrostatic energy ({Delta}U) as well as the total electronic energy of SCO molecules. Moreover, our calculated results demonstrate an important contribution of the interionic interactions to {Delta}U, and there is the relation between {Delta}U and the thermal hysteresis behavior of SCO molecules. These results should be helpful for developing new SCO molecules.

  19. Interplay between Landau-Zener transition dynamic and quantum phase transition in dissipative spin chain with Dzyaloshinsky-Moriya interaction

    Science.gov (United States)

    Diffo, J. T.; Ateuafack, M. E.; Fouokeng, G. C.; Fai, L. C.; Tchoffo, M.

    2017-11-01

    The paper investigates the transition dynamic of a two-level system coupled uniformly to a general XY dissipative spin-chain environment with the Dzyaloshinsky-Moriya interaction. The collective effect of the spin-chain environment is studied and we obtained the exact expression of the final occupation of the system. It is observed that the increase of the decay parameter favors a shortcut to adiabaticity. In the absence of decay, the transition probability oscillations are modulated in time by the renormalized Landau-Zener (LZ) parameter that we derived. We found that in the vicinity of the critical point of the environment, depending on the strength of the system-environment coupling, the decay of the population transfer can be tailored by tuning the other parameters of the model. The critical point and thus the occurrence of the phase transition are observed to be independent of these parameters. It is shown that this quantum state transition is related to the occurrence of the quantum phase transitions in the chain. The adiabatic change for the magnetization observed in some magnetic molecules may be due to the number of spin involved in the chain, the anisotropy parameter of the chain or the external magnetic field strength.

  20. Magnetic dipole transitions and spin currents in inelastic electron scattering

    Energy Technology Data Exchange (ETDEWEB)

    Lipas, P.O.; Koskinen, M. (Jyvaeskylae Univ. (Finland). Dept. of Physics); Harter, H.; Nojarov, R.; Faessler, A. (Tuebingen Univ. (Germany, F.R.). Inst. fuer Theoretische Physik)

    1989-10-26

    We use the microscopic interacting-boson approximation (IBA-2) to calculate the nuclear M1 transition current density for excitation by inelastic electron scattering. Although the strong 1{sup +} excitations are commonly regarded as due to proton convection, we find, with {sup 164}Dy as a test case, that proton and neutron spins cause strong oscillations in the current and are responsible for high-q-scattering. (orig.).

  1. Spin-orbit-induced spin splittings in polar transition metal dichalcogenide monolayers

    KAUST Repository

    Cheng, Yingchun

    2013-06-01

    The Rashba effect in quasi two-dimensional materials, such as noble metal surfaces and semiconductor heterostructures, has been investigated extensively, while interest in real two-dimensional systems has just emerged with the discovery of graphene. We present ab initio electronic structure, phonon, and molecular-dynamics calculations to study the structural stability and spin-orbit-induced spin splitting in the transition metal dichalcogenide monolayers MXY (M = Mo, W and X, Y = S, Se, Te). In contrast to the non-polar systems with X = Y, in the polar systems with X ≠ Y the Rashba splitting at the Γ-point for the uppermost valence band is caused by the broken mirror symmetry. An enhancement of the splitting can be achieved by increasing the spin-orbit coupling and/or the potential gradient. © Copyright EPLA, 2013.

  2. Observation of Longitudinal Spin Seebeck Effect with Various Transition Metal Films

    OpenAIRE

    Ishida, M.; Kirihara, A.; Someya, H.; Uchida, K.; Kohmoto, S.; Saitoh, E.; Murakami, T.

    2013-01-01

    We evaluated the thermoelectric properties of longitudinal spin Seebeck devices by using ten different transition metals (TMs). Both the intensity and sign of spin Seebeck coefficients were noticeably dependent on the degree of the inverse spin Hall effect and the resistivity of each TM film. Spin dependent behaviors were also observed under ferromagnetic resonance. These results indicate that the output of the spin Seebeck devices originates in the spin current.

  3. Hysteresis and change of transition temperature in thin films of Fe([Me{sub 2}Pyrz]{sub 3}BH){sub 2}, a new sublimable spin-crossover molecule

    Energy Technology Data Exchange (ETDEWEB)

    Davesne, V.; Gruber, M. [Institut de Physique et de Chimie des Matériaux de Strasbourg, UMR 7504 CNRS, Université de Strasbourg, 23 rue du Loess, 67034 Cedex 2 Strasbourg (France); Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Str. 1, 76131 Karlsruhe (Germany); Studniarek, M. [Institut de Physique et de Chimie des Matériaux de Strasbourg, UMR 7504 CNRS, Université de Strasbourg, 23 rue du Loess, 67034 Cedex 2 Strasbourg (France); Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP48, 91192 Gif-sur-Yvette (France); Doh, W. H.; Zafeiratos, S. [Institut de Chimie et Procédés pour l’Energie, l’Environnement et la Santé, UMR 7515 CNRS, Université de Strasbourg, 25 rue Becquerel, 67087 Cedex 2 Strasbourg (France); Joly, L.; Schmerber, G.; Bowen, M.; Weber, W.; Boukari, S.; Da Costa, V.; Arabski, J.; Beaurepaire, E. [Institut de Physique et de Chimie des Matériaux de Strasbourg, UMR 7504 CNRS, Université de Strasbourg, 23 rue du Loess, 67034 Cedex 2 Strasbourg (France); Sirotti, F.; Silly, M. G. [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP48, 91192 Gif-sur-Yvette (France); Gaspar, A. B.; Real, J. A. [Institut de Ciència Molecular (ICMol), Universitat de València, C/Catedrático José Beltrán Martínez 2, 46980 Paterna (València) (Spain); and others

    2015-05-21

    Thin films of the spin-crossover (SCO) molecule Fe([Me{sub 2}Pyrz]{sub 3}BH){sub 2} (Fe-pyrz) were sublimed on Si/SiO{sub 2} and quartz substrates, and their properties investigated by X-ray absorption and photoemission spectroscopies, optical absorption, atomic force microscopy, and superconducting quantum interference device. Contrary to the previously studied Fe(phen){sub 2}(NCS){sub 2}, the films are not smooth but granular. The thin films qualitatively retain the typical SCO properties of the powder sample (SCO, thermal hysteresis, soft X-ray induced excited spin-state trapping, and light induced excited spin-state trapping) but present intriguing variations even in micrometer-thick films: the transition temperature decreases when the thickness is decreased, and the hysteresis is affected. We explain this behavior in the light of recent studies focusing on the role of surface energy in the thermodynamics of the spin transition in nano-structures. In the high-spin state at room temperature, the films have a large optical gap (∼5 eV), decreasing at thickness below 50 nm, possibly due to film morphology.

  4. Spin-Peierls transition in low-dimensional quantum spin systems: a Green's function approach.

    Science.gov (United States)

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

    2009-12-28

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

  5. Ferroelasticity and spin-state transitions of LaCoO3

    Science.gov (United States)

    Araki, Wakako; Abe, Takehiro; Arai, Yoshio

    2014-07-01

    A uniaxial compression test of polycrystalline lanthanum cobaltite (LCO) was performed to investigate mechanical behavior of LCO in the temperature range of 83-553 K. Prepared by solid-state reaction, the electrical resistivity and the linear expansion coefficient of polycrystalline LCO, measured between 80 and 1273 K, exhibit distinct changes attributed to spin-state transitions of cobalt ions around 100-200 K and 400-600 K, but are relatively constant between 200 and 400 K. The stress-strain curve obtained under uniaxial compression shows strong nonlinearity due to ferroelastic domain switching process between 83 and 553 K. Initial Young's moduli, critical stress, and dissipated energy evaluated from the stress-strain curves decrease by about a half with increasing the temperature, whereas there was no drastic changes even around the spin-state transition temperatures. The initial modulus agrees with the temperature dependence of the apparent Young's modulus measured under low-stress cyclic loading.

  6. Tunable spin-charge conversion through topological phase transitions in zigzag nanoribbons

    KAUST Repository

    Li, Hang

    2016-06-29

    We study spin-orbit torques and charge pumping in magnetic quasi-one-dimensional zigzag nanoribbons with a hexagonal lattice, in the presence of large intrinsic spin-orbit coupling. Such a system experiences a topological phase transition from a trivial band insulator to a quantum spin Hall insulator by tuning of either the magnetization direction or the intrinsic spin-orbit coupling. We find that the spin-charge conversion efficiency (i.e., spin-orbit torque and charge pumping) is dramatically enhanced at the topological transition, displaying a substantial angular anisotropy.

  7. Phase Transitions in Electron Spin Resonance Under Continuous Microwave Driving

    Science.gov (United States)

    Karabanov, A.; Rose, D. C.; Köckenberger, W.; Garrahan, J. P.; Lesanovsky, I.

    2017-10-01

    We study an ensemble of strongly coupled electrons under continuous microwave irradiation interacting with a dissipative environment, a problem of relevance to the creation of highly polarized nonequilibrium states in nuclear magnetic resonance. We analyze the stationary states of the dynamics, described within a Lindblad master equation framework, at the mean-field approximation level. This approach allows us to identify steady-state phase transitions between phases of high and low polarization controlled by the distribution of disordered electronic interactions. We compare the mean-field predictions to numerically exact simulations of small systems and find good agreement. Our study highlights the possibility of observing collective phenomena, such as metastable states, phase transitions, and critical behavior, in appropriately designed paramagnetic systems. These phenomena occur in a low-temperature regime which is not theoretically tractable by conventional methods, e.g., the spin-temperature approach.

  8. Phenomenological Models of Photoinduced Transition in Spin-Crossover Materials

    Science.gov (United States)

    Gudyma, Iurii; Maksymov, Artur

    The stochastic kinetics of photoinduced transition in spin-crossover systems, as representatives of synthetic molecular magnetic materials, was reviewed. The focus has been done on the macroscopic phenomenological models, which were described by dynamic potential in terms of Lyapunov functions and obeys to Langevin kinetics with white and colored stochastic processes. By corresponding Fokker-Planck equation was studied the evolution of probability of system states. For the system with light-induced transition which is additionally driven by external periodic force it has been shown the possibility of resonance enhancement of magnetization at certain values of the amplitude of periodic signal and noise intensity. The stochastic resonance phenomenon was analyzed by signal-to-noise ratio for Markovian and non-Markovian noise, various amplitudes and frequencies of periodic signal, and also variation of noise intensity.

  9. Spin Transition Sensors Based on β-Amino-Acid 1,2,4-Triazole Derivative

    Directory of Open Access Journals (Sweden)

    Aurelian Rotaru

    2011-08-01

    Full Text Available A β-aminoacid ester was successfully derivatized to yield to 4H-1,2-4-triazol-4-yl-propionate (βAlatrz which served as a neutral bidentate ligand in the 1D coordination polymer [Fe(βAlatrz3](CF3SO32·0.5H2O (1·0.5H2O. The temperature dependence of the high-spin molar fraction derived from 57Fe Mossbauer spectroscopy recorded on cooling below room temperature reveals an exceptionally abrupt single step transition between high-spin and low-spin states with a hysteresis loop of width 4 K (Tc↑ = 232 K and Tc↓ = 228 K in agreement with magnetic susceptibility measurements. The material presents striking reversible thermochromism from white, at room temperature, to pink on quench cooling to liquid nitrogen, and acts as an alert towards temperature variations. The phase transition is of first order, as determined by differential scanning calorimetry, with transition temperatures matching the ones determined by SQUID and Mössbauer spectroscopy. The freshly prepared sample of 1·0.5H2O, dried in air, was subjected to annealing at 390 K, and the obtained white compound [Fe(βAlatrz3](CF3SO32 (1 was found to exhibit a similar spin transition curve however much temperature was increased by (Tc↑ = 252 K and Tc↓ = 248 K. The removal of lattice water molecules from 1·0.5H2O is not accompanied by a change of the morphology and of the space group, and the chain character is preserved. However, an internal pressure effect stabilizing the low-spin state is evidenced.

  10. Spin transition sensors based on β-amino-acid 1,2,4-triazole derivative.

    Science.gov (United States)

    Dîrtu, Marinela M; Schmit, France; Naik, Anil D; Rotaru, Aurelian; Marchand-Brynaert, J; Garcia, Yann

    2011-01-01

    A β-aminoacid ester was successfully derivatized to yield to 4H-1,2-4-triazol-4-yl-propionate (βAlatrz) which served as a neutral bidentate ligand in the 1D coordination polymer [Fe(βAlatrz)(3)](CF(3)SO(3))(2)·0.5H(2)O (1·0.5H(2)O). The temperature dependence of the high-spin molar fraction derived from (57)Fe Mossbauer spectroscopy recorded on cooling below room temperature reveals an exceptionally abrupt single step transition between high-spin and low-spin states with a hysteresis loop of width 4 K (T(c) (↑) = 232 K and T(c) (↓) = 228 K) in agreement with magnetic susceptibility measurements. The material presents striking reversible thermochromism from white, at room temperature, to pink on quench cooling to liquid nitrogen, and acts as an alert towards temperature variations. The phase transition is of first order, as determined by differential scanning calorimetry, with transition temperatures matching the ones determined by SQUID and Mössbauer spectroscopy. The freshly prepared sample of 1·0.5H(2)O, dried in air, was subjected to annealing at 390 K, and the obtained white compound [Fe(βAlatrz)(3)](CF(3)SO(3))(2) (1) was found to exhibit a similar spin transition curve however much temperature was increased by (T(c) (↑) = 252 K and T(c) (↓) = 248 K). The removal of lattice water molecules from 1·0.5H(2)O is not accompanied by a change of the morphology and of the space group, and the chain character is preserved. However, an internal pressure effect stabilizing the low-spin state is evidenced.

  11. A spinning thermometer to monitor microwave heating and glass transitions in dynamic nuclear polarization.

    Science.gov (United States)

    Miéville, Pascal; Vitzthum, Veronika; Caporini, Marc A; Jannin, Sami; Gerber-Lemaire, Sandrine; Bodenhausen, Geoffrey

    2011-11-01

    As previously demonstrated by Thurber and Tycko, the peak position of (79)Br in potassium bromide (KBr) allows one to determine the temperature of a spinning sample. We propose to adapt the original design by using a compact KBr tablet placed at the bottom of the magic angle spinning rotor, separated from the sample under investigation by a thin disk made of polytetrafluoroethylene (or 'Teflon'®). This design allows spinning the sample up to at least 16 kHz. The KBr tablet can remain in the rotor when changing the sample under investigation. Calibration in the range of 98 nuclear polarization enhancement decreases with increasing temperature, in particular when a frozen glassy sample undergoes a glass transition. Copyright © 2011 John Wiley & Sons, Ltd.

  12. Nonequilibrium Phase Transition in Spin-S Ising Ferromagnet Driven by Propagating and Standing Magnetic Field Wave

    Science.gov (United States)

    Halder, Ajay; Acharyya, Muktish

    2017-11-01

    The dynamical response of spin-S (S=1, 3/2, 2, 3) Ising ferromagnet to the plane propagating wave, standing magnetic field wave and uniformly oscillating field with constant frequency are studied separately in two dimensions by extensive Monte Carlo simulation. Depending upon the strength of the magnetic field and the value of the spin state of the Ising spin lattice two different dynamical phases are observed. For a fixed value of S and the amplitude of the propagating magnetic field wave the system undergoes a dynamical phase transition from propagating phase to pinned phase as the temperature of the system is cooled down. Similarly in case with standing magnetic wave the system undergoes dynamical phase transition from high temperature phase where spins oscillate coherently in alternate bands of half wavelength of the standing magnetic wave to the low temperature pinned or spin frozen phase. For a fixed value of the amplitude of magnetic field oscillation the transition temperature is observed to decrease to a limiting value as the value of spin S is increased. The time averaged magnetisation over a full cycle of the magnetic field oscillation plays the role of the dynamic order parameter. A comprehensive phase boundary is drawn in the plane of magnetic field amplitude and dynamic transition temperature. It is found that the phase boundary shrinks inwards for high value of spin state S. Also in the low temperature (and high field) region the phase boundaries are closely spaced.

  13. Phase transition in IrTe2 induced by spin-orbit coupling

    Science.gov (United States)

    Koley, S.

    2016-12-01

    IrTe2 has been renewed as an interesting system showing competing phenomenon between a questionable density-wave transition near 270 K followed by superconductivity with doping of high atomic number materials. Higher atomic numbers of Te and Ir supports strong spin-orbital coupling in this system. Using dynamical mean field theory with LDA band structure I have introduced Rashba spin orbit coupling in this system to get the interpretation for anomalous resistivity and related transition in this system. While no considerable changes are observed in DMFT results of Ir-5d band other than orbital selective pseudogap 'pinned' to Fermi level, Te-p band shows a van Hove singularity at the Fermi level except low temperature. Finally I discuss the implications of these results in theoretical understanding of ordering in IrTe2.

  14. Influence of an electric field on the spin-reorientation transition in Ni/Cu(100)

    Energy Technology Data Exchange (ETDEWEB)

    Gerhard, Lukas [Institut für Nanotechnologie, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen (Germany); Bonell, Frédéric; Suzuki, Yoshishige [CREST, Japan Science Technology, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Graduate School of Engineering Science, Osaka University, Osaka 560-8531 (Japan); Wulfhekel, Wulf [Institut für Nanotechnologie, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen (Germany); Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe (Germany)

    2014-10-13

    Magnetoelectric coupling offers the possibility to change the magnetic state of a material by an applied electric field. Over the last few years, metallic systems have come up as simple prototypes for this interaction. While the previous studies focused on Fe and Co thin films or their alloys, here we demonstrate magnetoelectric coupling in a Ni thin film which is close to a spin-reorientation transition. Our magneto-optic Kerr effect measurements on 10 ML of Ni/Cu(100) show a considerable influence of the applied electric field on the magnetism. This rounds off the range of magnetic metals that exhibit magnetoelectric coupling, and it reveals the possibility of an electric field control of a spin-reorientation transition.

  15. Large spin splitting in the conduction band of transition metal dichalcogenide monolayers

    Science.gov (United States)

    Kośmider, K.; González, J. W.; Fernández-Rossier, J.

    2013-12-01

    We study the conduction band spin splitting that arises in transition metal dichalcogenide (TMD) semiconductor monolayers such as MoS2,MoSe2, WS2, and WSe2 due to the combination of spin-orbit coupling and lack of inversion symmetry. Two types of calculation are done. First, density functional theory (DFT) calculations based on plane waves that yield large splittings, between 3 and 30 meV. Second, we derive a tight-binding model that permits to address the atomic origin of the splitting. The basis set of the model is provided by the maximally localized Wannier orbitals, obtained from the DFT calculation, and formed by 11 atomiclike orbitals corresponding to d and p orbitals of the transition metal (W, Mo) and chalcogenide (S, Se) atoms respectively. In the resulting Hamiltonian, we can independently change the atomic spin-orbit coupling constant of the two atomic species at the unit cell, which permits to analyze their contribution to the spin splitting at the high symmetry points. We find that—in contrast to the valence band—both atoms give comparable contributions to the conduction band splittings. Given that these materials are most often n-doped, our findings are important for developments in TMD spintronics.

  16. Thin film magnetoelectric composites near spin reorientation transition

    Energy Technology Data Exchange (ETDEWEB)

    Tiercelin, N. [Joint European Laboratory LEMAC: IEMN CNRS 8520-Ecole Centrale de Lille, Villeneuve d' Ascq 59652 (France)], E-mail: Nicolas.Tiercelin@iemn.univ-lille1.fr; Preobrazhensky, V. [Joint European Laboratory LEMAC: IEMN CNRS 8520-Ecole Centrale de Lille, Villeneuve d' Ascq 59652 (France); Joint European Laboratory LEMAC: WRC-GPI-RAS 117454, Vernadsky prosp. 78, Moscow (Russian Federation); Mortet, V. [Institute for Materials Research (IMO), Hasselt University, IMEC vzw, Division IMOMEC, B-3590 Diepenbeek (Belgium); Talbi, A. [Joint European Laboratory LEMAC: IEMN CNRS 8520-Ecole Centrale de Lille, Villeneuve d' Ascq 59652 (France); Soltani, A. [IEMN CNRS 8520, Bd Poincare, Villeneuve d' Ascq 59651 (France); Haenen, K. [Institute for Materials Research (IMO), Hasselt University, IMEC vzw, Division IMOMEC, B-3590 Diepenbeek (Belgium); Pernod, P. [Joint European Laboratory LEMAC: IEMN CNRS 8520-Ecole Centrale de Lille, Villeneuve d' Ascq 59652 (France)

    2009-06-15

    We report the use of a magnetic instability of the spin reorientation transition type to enhance the magnetoelectric sensitivity in magnetostrictive-piezoelectric structures. We present the theoretical study of a clamped beam resonant actuator composed of a piezoelectric element on a passive substrate actuated by a magnetostrictive nanostructured layer. The experiments were made on a polished 150 {mu}m thick 18x3 mm{sup 2} lead zirconate titanate (PZT) plate glued to a 50 {mu}m thick silicon plate and coated with a giant magnetostrictive nanostructured Nx(TbCo{sub 25nm}/FeCo{sub 5nm}) layer. A second set of experiments was done with magnetostrictive layer deposited on PZT plate. Finally, a film/film structure using magnetostrictive and aluminium nitride films on silicon substrate was realized, and showed ME amplitudes reaching 30 V Oe{sup -1} cm{sup -1}. Results agree with analytical theory.

  17. Thin film magnetoelectric composites near spin reorientation transition

    Science.gov (United States)

    Tiercelin, N.; Preobrazhensky, V.; Mortet, V.; Talbi, A.; Soltani, A.; Haenen, K.; Pernod, P.

    2009-06-01

    We report the use of a magnetic instability of the spin reorientation transition type to enhance the magnetoelectric sensitivity in magnetostrictive-piezoelectric structures. We present the theoretical study of a clamped beam resonant actuator composed of a piezoelectric element on a passive substrate actuated by a magnetostrictive nanostructured layer. The experiments were made on a polished 150 μm thick 18×3 mm 2 lead zirconate titanate (PZT) plate glued to a 50 μm thick silicon plate and coated with a giant magnetostrictive nanostructured Nx(TbCo 2 5nm/FeCo 5nm) layer. A second set of experiments was done with magnetostrictive layer deposited on PZT plate. Finally, a film/film structure using magnetostrictive and aluminium nitride films on silicon substrate was realized, and showed ME amplitudes reaching 30 V Oe -1 cm -1. Results agree with analytical theory.

  18. 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 ...

  19. Spin reorientation transition in Co/Au multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Quispe-Marcatoma, J., E-mail: jquispem@unmsm.edu.pe [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro 22290-180 (Brazil); Facultad de Ciencias Físicas, Universidad Nacional Mayor de San Marcos, P.O. Box 14-0149, Lima 14, Perú (Peru); Tarazona, H. [Facultad de Ciencias Físicas, Universidad Nacional Mayor de San Marcos, P.O. Box 14-0149, Lima 14, Perú (Peru); Pandey, B. [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro 22290-180 (Brazil); Department of Applied Science, Symbiosis Institute of Technology, SIU, Lavale, Pune 412 115, India. (India); Sousa, M.A. de [Instituto de Física, Universidade Federal de Goiás, Goiânia 74001-970 (Brazil); Carvalho, M. [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro 22290-180 (Brazil); Landauro, C.V. [Facultad de Ciencias Físicas, Universidad Nacional Mayor de San Marcos, P.O. Box 14-0149, Lima 14, Perú (Peru); Pelegrini, F. [Instituto de Física, Universidade Federal de Goiás, Goiânia 74001-970 (Brazil); Baggio Saitovitch, E. [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro 22290-180 (Brazil)

    2014-10-01

    We report a study about the spin reorientation transition (SRT) from perpendicular easy axis to in-plane easy axis of magnetization in Co/Au multilayers. A series of multilayers of Si/Au(100 Å)/{[Co(t_C_o)/Au(20 Å)]_2_0}/Au(50 Å) family were studied, with Co layer thickness varying between 6 Å to 30 Å. The thickness of the Au layer was chosen large enough in order to minimize the interlayer exchange coupling between Co layers. In such thick Au-layer samples the magnetic properties are mainly the result of competition between interlayer magnetostatic coupling due to stray field, perpendicular magnetic anisotropy and shape anisotropy. The effective anisotropy constant K{sub eff} and the second order anisotropy K{sub 2} were deduced from the fit of the resonant magnetic field obtained from out of plane dependence Ferromagnetic Resonance (FMR) experiments. To study the SRT, we have plotted the phase diagram between K{sub eff} and K{sub 2}. The results show that SRT occurs through the metastable region with K{sub 2} ≤ −½ K{sub eff}, (K{sub eff} > 0). It is interesting to note that FMR shows the coexistence of two modes with different anisotropy for small Co thickness, while for thick Co layers the modes have the same anisotropy. Moreover, in thick Co layer samples, volume and surface spin wave resonance (SWR) modes were also excited by the microwave field, around the perpendicular FMR geometry, giving a clear evidence of a magnetic coupling between the Co layers. - Highlights: • Co/Au multilayers with varying Co layer thickness are prepared by DC-magnetron sputtering. • The spin reorientation transition (SRT) and flipping of magnetic moment are studied. • Effective anisotropy constant (K) and 2nd order anisotropy constant (K{sub 2}) are calculated. • K Vs K{sub 2} plot showed that SRT occurs through the metastable region with K{sub 2} ≤ −½ K, (K > 0). • Ferromagnetic Resonance spectra showed the coexistence of two resonance modes.

  20. Organizational Transition and Change Resistance

    Directory of Open Access Journals (Sweden)

    Ciprian Nicolescu

    2006-09-01

    Full Text Available The paper focuses on the very important atopic of organizational transition and change resistance. It is divided in four parts. The first part deals with transition inevitability and its content in the change process. The second part of the paper refers to the change resistance. After a short presentation of a recent approach of this topic, elaborated by Rick Maurer, the authors present their point of view, identifying 14 main causes refering to the main factors involved in the organizational transition. In the third part, authors have formulated a set of key elements which should be taken into consideration in order to achieve a rapid and succesful organizational changes. These key elements are valable for any type of organization – entreprise, institution, locality, region, country a.s.a. The last part of the study deals with conflicts approach, which appear almost always during organizational transition. The conflicts are separated in three categories and for whom are presented the methodes recommended in order to solve them with good results.

  1. Transition from spin-orbit to hyperfine interaction dominated spin relaxation in a cold fluid of dipolar excitons

    Science.gov (United States)

    Finkelstein, Ran; Cohen, Kobi; Jouault, Benoit; West, Ken; Pfeiffer, Loren N.; Vladimirova, Masha; Rapaport, Ronen

    2017-08-01

    We measure the spin-resolved transport of dipolar excitons in a biased GaAs double quantum well structure. From these measurements we extract both spin lifetime and mobility of the excitons. We find that below a temperature of 4.8 K there is a sharp increase in the spin lifetime of the excitons, together with a sharp reduction in their mobility. Below a critical power the spin lifetime increases with increasing mobility and density, while above the critical power the opposite trend is observed. We interpret this transition as evidence of the interplay between two different spin dephasing mechanisms: at low mobility the dephasing is dominated by the hyperfine interaction with the lattice nuclei spins, while at higher mobility the spin-orbit interaction dominates and a Dyakonov-Perel spin relaxation takes over. The excitation power and temperature regime where the hyperfine interaction induced spin dephasing is observed correlates with the regime where a dark dipolar quantum liquid was reported recently on a similar sample.

  2. One and Two Phonon Assisted Transitions between Exciton Spin States in a Quantum Dot

    Science.gov (United States)

    Roszak, K.; Machnikowski, P.; Axt, V. M.; Kuhn, T.

    2008-11-01

    Exciton spin decay is studied in a self-assembled InAs/GaAs quantum dot. The spin relaxation results from an interplay of two factors: the Bir-Pikus Hamiltonian and the short-range exchange interaction, leading to one and two phonon assisted transitions. We establish a hierarchy between the resulting transition rates and show the dominating role of transverse phonons for all the transitions.

  3. Spatiotemporal dynamics of the spin transition in [Fe (HB(tz)3) 2] single crystals

    Science.gov (United States)

    Ridier, Karl; Rat, Sylvain; Shepherd, Helena J.; Salmon, Lionel; Nicolazzi, William; Molnár, Gábor; Bousseksou, Azzedine

    2017-10-01

    The spatiotemporal dynamics of the spin transition have been thoroughly investigated in single crystals of the mononuclear spin-crossover (SCO) complex [Fe (HB (tz )3)2] (tz = 1 ,2 ,4-triazol-1-yl) by optical microscopy. This compound exhibits an abrupt spin transition centered at 334 K with a narrow thermal hysteresis loop of ˜1 K (first-order transition). Most single crystals of this compound reveal exceptional resilience upon repeated switching (several hundred cycles), which allowed repeatable and quantitative measurements of the spatiotemporal dynamics of the nucleation and growth processes to be carried out. These experiments revealed remarkable properties of the thermally induced spin transition: high stability of the thermal hysteresis loop, unprecedented large velocities of the macroscopic low-spin/high-spin phase boundaries up to 500 µm/s, and no visible dependency on the temperature scan rate. We have also studied the dynamics of the low-spin → high-spin transition induced by a local photothermal excitation generated by a spatially localized (Ø = 2 μ m ) continuous laser beam. Interesting phenomena have been evidenced both in quasistatic and dynamic conditions (e.g., threshold effects and long incubation periods, thermal activation of the phase boundary propagation, stabilization of the crystal in a stationary biphasic state, and thermal cutoff frequency). These measurements demonstrated the importance of thermal effects in the transition dynamics, and they enabled an accurate determination of the thermal properties of the SCO compound in the framework of a simple theoretical model.

  4. Optimal Charge-to-Spin Conversion in Graphene on Transition-Metal Dichalcogenides

    Science.gov (United States)

    Offidani, Manuel; Milletarı, Mirco; Raimondi, Roberto; Ferreira, Aires

    2017-11-01

    When graphene is placed on a monolayer of semiconducting transition metal dichalcogenide (TMD) its band structure develops rich spin textures due to proximity spin-orbital effects with interfacial breaking of inversion symmetry. In this work, we show that the characteristic spin winding of low-energy states in graphene on a TMD monolayer enables current-driven spin polarization, a phenomenon known as the inverse spin galvanic effect (ISGE). By introducing a proper figure of merit, we quantify the efficiency of charge-to-spin conversion and show it is close to unity when the Fermi level approaches the spin minority band. Remarkably, at high electronic density, even though subbands with opposite spin helicities are occupied, the efficiency decays only algebraically. The giant ISGE predicted for graphene on TMD monolayers is robust against disorder and remains large at room temperature.

  5. Phase transitions in continuum ferromagnets with unbounded spins

    Energy Technology Data Exchange (ETDEWEB)

    Daletskii, Alexei, E-mail: alex.daletskii@york.ac.uk [Department of Mathematics, University of York, York YO10 DD (United Kingdom); Kondratiev, Yuri, E-mail: kondrat@math.uni-bielefeld.de [Fakultät für Mathematik, Universität Bielefeld, Bielefeld D-33615 (Germany); Kozitsky, Yuri, E-mail: jkozi@hektor.umcs.lublin.pl [Instytut Matematyki, Uniwersytet Marii Curie-Skłodowskiej, 20-031 Lublin (Poland)

    2015-11-15

    States of thermal equilibrium of an infinite system of interacting particles in ℝ{sup d} are studied. The particles bear “unbounded” spins with a given symmetric a priori distribution. The interaction between the particles is pairwise and splits into position-position and spin-spin parts. The position-position part is described by a superstable potential, and the spin-spin part is attractive and of finite range. Thermodynamic states of the system are defined as tempered Gibbs measures on the space of marked configurations. It is proved that the set of such measures contains at least two elements if the activity is big enough.

  6. Investigation of metabolite changes in the transition from pre-invasive to invasive cervical cancer measured using (1)H and (31)P magic angle spinning MRS of intact tissue.

    Science.gov (United States)

    De Silva, Sonali S; Payne, Geoffrey S; Thomas, Valerie; Carter, Paul G; Ind, Thomas E J; deSouza, Nandita M

    2009-02-01

    The aim of this study was to determine the metabolic changes in the transition from pre-invasive to invasive cervical cancer using high-resolution magic angle spinning (HR-MAS) MRS. Biopsy specimens were obtained from women with histologically normal cervix (n = 5), cervical intraepithelial neoplasia (CIN; mild, n = 5; moderate/severe, n = 40), and invasive cancer (n = 23). (1)H HR-MAS MRS data were acquired using a Bruker Avance 11.74 T spectrometer (Carr-Purcell-Meiboom-Gill sequence; TR = 4.8 s; TE = 135 ms; 512 scans; 41 min acquisition). (31)P HR-MAS spectra were obtained from the normal subjects and cancer patients only (as acetic acid applied before tissue sampling in patients with CIN impaired spectral quality) using a (1)H-decoupled pulse-acquire sequence (TR = 2.82 s; 2048 scans; 96 min acquisition). Peak assignments were based on values reported in the literature. Peak areas were measured using the AMARES algorithm. Estimated metabolite concentrations were compared between patient diagnostic categories and tissue histology using independent samples t tests. Comparisons based on patient category at diagnosis showed significantly higher estimated concentrations of choline (P = 0.0001) and phosphocholine (P = 0.002) in tissue from patients with cancer than from patients with high-grade dyskaryosis, but no differences between non-cancer groups. Division by histology of the sample also showed increases in choline (P = 0.002) and phosphocholine (P = 0.002) in cancer compared with high-grade CIN tissue. Phosphoethanolamine was increased in cancer compared with normal tissue (P = 0.0001). Estimated concentrations of alanine (P = 0.01) and creatine (P = 0.008) were significantly reduced in normal tissue from cancer patients compared with normal tissue from non-cancer patients. The estimated concentration of choline was significantly increased in CIN tissue from cancer patients compared with CIN tissue from non-cancer patients (P = 0.0001). Estimated

  7. Squeezing giant spin states via geometric phase control in cavity-assisted Raman transitions.

    Science.gov (United States)

    Xia, Keyu

    2017-10-09

    Squeezing ensemble of spins provides a way to surpass the standard quantum limit in quantum metrology and test the fundamental physics as well, and therefore attracts broad interest. Here we propose an experimentally accessible protocol to squeeze a giant ensemble of spins via the geometric phase control (GPC). Using the cavity-assisted Raman transition (CART) in a double Λ-type system, we realize an effective Dicke model. Under the condition of vanishing effective spin transition frequency, we find a particular evolution time where the cavity decouples from the spins and the spin ensemble is squeezed considerably. Our scheme combines the CART and the GPC, and has the potential to improve the sensitivity in quantum metrology with spins by about two orders.

  8. Spin transition of ferric iron in the calcium-ferrite type aluminous phase: Fe 3+ Spin Transition in the CF Phase

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Ye [School of Science, Wuhan University of Technology, Wuhan China; Qin, Fei [Key Laboratory of Orogenic Belts and Crustal Evolution, MOE, and School of Earth and Space Sciences, Peking University, Beijing China; Wu, Xiang [State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan China; Huang, Haijun [School of Science, Wuhan University of Technology, Wuhan China; McCammon, Catherine A. [Bayerisches Geoinstitut, Universität Bayreuth, Bayreuth Germany; Yoshino, Takashi [Institute for Planetary Materials, Okayama University, Misasa Japan; Zhai, Shuangmeng [Key Laboratory of High-temperature and High-pressure Study of the Earth' s Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang China; Xiao, Yuming [HPCAT, Geophysical Laboratory, Carnegie Institution of Washington, Argonne Illinois USA; Prakapenka, Vitali B. [GeoSoilEnviroCARS, University of Chicago, Chicago Illinois USA

    2017-08-01

    We investigated Fe-free and Fe-bearing CF phases using nuclear forward scattering and X-ray diffraction coupled with diamond anvil cells up to 80 GPa at room temperature. Octahedral Fe3+ ions in the Fe-bearing CF phase undergo a high-spin to low-spin transition at 25–35 GPa, accompanied by a volume reduction of ~2.0% and a softening of bulk sound velocity up to 17.6%. Based on the results of this study and our previous studies, both the NAL and CF phases, which account for 10–30 vol % of subducted MORB in the lower mantle, are predicted to undergo a spin transition of octahedral Fe3+ at lower mantle pressures. Spin transitions in these two aluminous phases result in an increase of density of 0.24% and a pronounced softening of bulk sound velocity up to 2.3% for subducted MORB at 25–60 GPa and 300 K. The anomalous elasticity region expands and moves to 30–75 GPa at 1200 K and the maximum of the VΦ reduction decreases to ~1.8%. This anomalous elastic behavior of Fe-bearing aluminous phases across spin transition zones may be relevant in understanding the observed seismic signatures in the lower mantle.

  9. Picture change error in quasirelativistic electron/spin density, Laplacian and bond critical points

    KAUST Repository

    Bučinský, Lukáš

    2014-06-01

    The change of picture of the quasirelativistic Hartree-Fock wave functions is considered for electron/spin densities, the negative Laplacian of electron density and the appropriate bond critical point characteristics from the Quantum Theory of Atoms In Molecules (QTAIM). [OsCl5(Hpz)]- and [RuCl5(NO)]2- transition metal complexes are considered. Both, scalar relativistic and spin-orbit effects have been accounted for using the Infinite Order Two Component (IOTC) Hamiltonian. Picture change error (PCE) correction in the electron and spin densities and the Laplacian of electron density are treated analytically. Generally, PCE is found significant only in the core region of the atoms for the electron/spin density as well as Laplacian.©2014 Elsevier B.V. All rights reserved.

  10. Spin Structure Change in Co-Substituted BiFeO3

    Science.gov (United States)

    Yamamoto, Hajime; Kihara, Takumi; Oka, Kengo; Tokunaga, Masashi; Mibu, Ko; Azuma, Masaki

    2016-06-01

    The spin structure in BiFe1-xCoxO3 (x = 0.05,0.10,0.15,0.20) was investigated as a function of Co substitution, temperature, and magnetic field. It was found that the cycloidal spin structure of BiFeO3 changed to a collinear one with spin canting and composition-independent spontaneous magnetization of ˜0.25 μB/f.u. for the Co substituted samples on heating. The collinear phase was stabilized under magnetic fields. The spin structure change was clarified also by the temperature dependence of 57Fe Mössbauer spectra, and the results indicated the first order nature of this transition.

  11. Managing Change and Transition, Creating a Future

    Science.gov (United States)

    Liu, Karen

    2008-01-01

    Beginning in childhood and on into adulthood, people experience many transitions and changes in their lives. Some people cope with change better than others and make transitions easily; some people may experience a longer transition in order to integrate change. Most people have a fear of change due to uncertainty. Once a person releases that…

  12. Study of pressure influence on thermal transition in spin-crossover nanomaterials

    National Research Council Canada - National Science Library

    Gudyma, Iurii V; Maksymov, Artur Iu; Ivashko, Victor V

    2014-01-01

    The thermal transition accompanied by the variation of the molecular volume in nanoparticles of spin-crossover materials has been studied on the basis of microscopic Ising-like model solved using Monte Carlo methods...

  13. Nonequilibrium effective field theory for absorbing state phase transitions in driven open quantum spin systems

    Science.gov (United States)

    Buchhold, Michael; Everest, Benjamin; Marcuzzi, Matteo; Lesanovsky, Igor; Diehl, Sebastian

    2017-01-01

    Phase transitions to absorbing states are among the simplest examples of critical phenomena out of equilibrium. The characteristic feature of these models is the presence of a fluctuationless configuration which the dynamics cannot leave, which has proved a rather stringent requirement in experiments. Recently, a proposal to seek such transitions in highly tunable systems of cold-atomic gases offers to probe this physics and, at the same time, to investigate the robustness of these transitions to quantum coherent effects. Here, we specifically focus on the interplay between classical and quantum fluctuations in a simple driven open quantum model which, in the classical limit, reproduces a contact process, which is known to undergo a continuous transition in the "directed percolation" universality class. We derive an effective long-wavelength field theory for the present class of open spin systems and show that, due to quantum fluctuations, the nature of the transition changes from second to first order, passing through a bicritical point which appears to belong instead to the "tricritical directed percolation" class.

  14. Symmetry protected topological phases in spin-1 ladders and their phase transitions

    OpenAIRE

    Chen, Ji-Yao; Liu, Zheng-Xin

    2015-01-01

    We study two-legged spin-1 ladder systems with $D_2\\times \\sigma$ symmetry group, where $D_2$ is discrete spin rotational symmetry and $\\sigma$ means interchain reflection symmetry. The system has one trivial phase and seven nontrivial symmetry protected topological (SPT) phases. We construct Hamiltonians to realize all of these SPT phases and study the phase transitions between them. Our numerical results indicate that there is no direct continuous transition between any two SPT phases we st...

  15. Study of pressure influence on thermal transition in spin-crossover nanomaterials

    OpenAIRE

    Gudyma, Iurii V; Maksymov, Artur Iu; Ivashko, Victor V.

    2014-01-01

    The thermal transition accompanied by the variation of the molecular volume in nanoparticles of spin-crossover materials has been studied on the basis of microscopic Ising-like model solved using Monte Carlo methods. For considered model, we examined the spin-crossover phenomenon with applied hydrostatic pressure and thus was shown the possibility to shift transition temperature toward its room value. The obtained results of numerical simulations are in agreement with the experimental ones.

  16. Study of pressure influence on thermal transition in spin-crossover nanomaterials.

    Science.gov (United States)

    Gudyma, Iurii V; Maksymov, Artur Iu; Ivashko, Victor V

    2014-12-01

    The thermal transition accompanied by the variation of the molecular volume in nanoparticles of spin-crossover materials has been studied on the basis of microscopic Ising-like model solved using Monte Carlo methods. For considered model, we examined the spin-crossover phenomenon with applied hydrostatic pressure and thus was shown the possibility to shift transition temperature toward its room value. The obtained results of numerical simulations are in agreement with the experimental ones.

  17. Study of pressure influence on thermal transition in spin-crossover nanomaterials

    Science.gov (United States)

    Gudyma, Iurii V.; Maksymov, Artur Iu; Ivashko, Victor V.

    2014-12-01

    The thermal transition accompanied by the variation of the molecular volume in nanoparticles of spin-crossover materials has been studied on the basis of microscopic Ising-like model solved using Monte Carlo methods. For considered model, we examined the spin-crossover phenomenon with applied hydrostatic pressure and thus was shown the possibility to shift transition temperature toward its room value. The obtained results of numerical simulations are in agreement with the experimental ones.

  18. Spin decoherence of a confined exciton due to one- and two-phonon assisted transitions

    Science.gov (United States)

    Roszak, K.; Machnikowski, P.; Axt, V. M.; Kuhn, T.

    2010-01-01

    Exciton spin decay in a self-assembled InAs/GaAs quantum dot is studied. The spin relaxation results from an interplay of two factors: the Bir-Pikus Hamiltonian and the short-range exchange interaction, leading to one- and two-phonon assisted transitions. We establish a hierarchy between the resulting transition rates; the one-phonon assisted transition to dark states is the fastest process. We also show the dominating role of transverse phonons for all of the transitions.

  19. Spin waves and the order-disorder transition in chromium

    DEFF Research Database (Denmark)

    Als-Nielsen, Jens Aage; Dietrich, O.W.

    1969-01-01

    The inelastic magnetic scattering of neutrons has been studied in Cr and Cr0.95-Mn0.05 both below and above the Neel temperature. The temperature dependence of the spin-wave velocity in the alloy has been measured below TN. The scattering above TN may also be interpreted in terms of spin-wavelike...

  20. Quantum spin/valley Hall effect and topological insulator phase transitions in silicene

    KAUST Repository

    Tahir, M.

    2013-04-26

    We present a theoretical realization of quantum spin and quantum valley Hall effects in silicene. We show that combination of an electric field and intrinsic spin-orbit interaction leads to quantum phase transitions at the charge neutrality point. This phase transition from a two dimensional topological insulator to a trivial insulating state is accompanied by a quenching of the quantum spin Hall effect and the onset of a quantum valley Hall effect, providing a tool to experimentally tune the topological state of silicene. In contrast to graphene and other conventional topological insulators, the proposed effects in silicene are accessible to experiments.

  1. Quantum phase transition in a far-from-equilibrium steady state of an XY spin chain.

    Science.gov (United States)

    Prosen, Tomaz; Pizorn, Iztok

    2008-09-05

    Using quantization in the Fock space of operators, we compute the nonequilibrium steady state in an open Heisenberg XY spin 1/2 chain of a finite but large size coupled to Markovian baths at its ends. Numerical and theoretical evidence is given for a far-from-equilibrium quantum phase transition with the spontaneous emergence of long-range order in spin-spin correlation functions, characterized by a transition from saturation to linear growth with the size of the entanglement entropy in operator space.

  2. Theoretical investigation on dye sensitizer solar cell: Spin-forbidden transition

    Energy Technology Data Exchange (ETDEWEB)

    Imamura, Yutaka [RIKEN, Advanced Institute for Computational Science, 7-1-26, Minatojima-minami-machi, Chuo-ku, Kobe, Hyogo 650-0047RIKEN (Japan)

    2015-12-31

    We studied spin-forbidden transitions of metal polypyridyl sensitizers by two-component relativistic time-dependent density functional theory with the spin-orbit interaction based on Tamm-Dancoff approximation. The singlet-to-triplet transition, which is assigned to a metal-to-ligand charge-transfer type excitation, appears for a phosphine-coordinated Ru(II), DX1. Absorption spectra of the modified DX1 molecules, whose Ru is replaced with Fe and Os, were also calculated for examining the effects of metals on the spin-orbit interaction.

  3. Spin and Valley Physics in Two Dimensional Systems: Graphene and Superconducting Transition Metal Dichalcogenides

    Science.gov (United States)

    Sosenko, Evan Boyd

    Recent focus on two dimensional materials and spin-coupled phenomena holds future potential for fast, efficient, flexible, and transparent devices. The fundamental operation of a spintronic device depends on the injection, transmission, and detection of spins in a conducting channel. Long spin lifetimes during transit are critical for realizing this technology. An attractive platform for this purpose is graphene, which has high mobilities and low spin-orbit coupling. Unfortunately, measured spin lifetimes are orders of magnitude smaller than theoretically expected. A source of spin loss is the resistance mismatch between the ferromagnetic electrodes and graphene. While this has been studied numerically, here we provide a closed form expression for Hanle spin precession which is the standard method of measuring spin lifetimes. This allows for a detailed characterization of the nonlocal spin valve device. Strong spin-orbit interaction has the potential to engender unconventional superconducting states. A cousin to graphene, two dimensional transition metal dichalcogenides entwine interaction, spin-orbit coupling, and topology. The noninteracting electronic states have multiple valleys in the energy dispersion and are topologically nontrivial. We report on the possible superconducting states of hole-doped systems, and analyze to what extent the correlated phase inherits the topological aspects of the parent crystal. We find that local attractive interactions or proximal coupling to s-wave superconductors lead to a pairing which is an equal mixture of a spin singlet and the m = 0 spin triplet. Its topology allows quasiparticle excitations of net nonzero Berry curvature via pair-breaking by circularly polarized light. The valley contrasting optical response, where oppositely circularly polarized light couples to different valleys, is present even in the superconducting state, though with smaller magnitude.

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

    Science.gov (United States)

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

    2017-08-01

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

  5. Driven spin transitions in fluorinated single- and bilayer-graphene quantum dots

    Science.gov (United States)

    Żebrowski, D. P.; Peeters, F. M.; Szafran, B.

    2017-06-01

    Spin transitions driven by a periodically varying electric potential in dilute fluorinated graphene quantum dots are investigated. Flakes of monolayer graphene as well as electrostatic electron traps induced in bilayer graphene are considered. The stationary states obtained within the tight-binding approach are used as the basis for description of the system dynamics. The dilute fluorination of the top layer lifts the valley degeneracy of the confined states and attenuates the orbital magnetic dipole moments due to current circulation within the flake. The spin-orbit coupling introduced by the surface deformation of the top layer induced by the adatoms allows the spin flips to be driven by the AC electric field. For the bilayer quantum dots the spin flip times is substantially shorter than the spin relaxation. Dynamical effects including many-photon and multilevel transitions are also discussed.

  6. k-asymmetric spin splitting at the interface between transition metal ferromagnets and heavy metals

    KAUST Repository

    Grytsiuk, Sergii

    2016-05-23

    We systematically investigate the spin-orbit coupling-induced band splitting originating from inversion symmetry breaking at the interface between a Co monolayer and 4d (Tc, Ru, Rh, Pd, and Ag) or 5d (Re, Os, Ir, Pt, and Au) transition metals. In spite of the complex band structure of these systems, the odd-in-k spin splitting of the bands displays striking similarities with the much simpler Rashba spin-orbit coupling picture. We establish a clear connection between the overall strength of the odd-in-k spin splitting of the bands and the charge transfer between the d orbitals at the interface. Furthermore, we show that the spin splitting of the Fermi surface scales with the induced orbital moment, weighted by the spin-orbit coupling.

  7. High-frequency EPR on high-spin transition-metal sites

    NARCIS (Netherlands)

    Mathies, Guinevere

    2012-01-01

    The electronic structure of transition-metal sites can be probed by electron-paramagnetic-resonance (EPR) spectroscopy. The study of high-spin transition-metal sites benefits from EPR spectroscopy at frequencies higher than the standard 9.5 GHz. However, high-frequency EPR is a developing field. In

  8. Thermodynamical analysis of spin-state transitions in LaCo O3 : Negative energy of mixing to assist thermal excitation to the high-spin excited state

    Science.gov (United States)

    Kyômen, Tôru; Asaka, Yoshinori; Itoh, Mitsuru

    2005-01-01

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

  9. Addressing spin transitions on 209Bi donors in silicon using circularly polarized microwaves

    Science.gov (United States)

    Yasukawa, T.; Sigillito, A. J.; Rose, B. C.; Tyryshkin, A. M.; Lyon, S. A.

    2016-03-01

    Over the past decade, donor spin qubits in isotopically enriched 28Si have been intensely studied due to their exceptionally long coherence times. More recently, bismuth donor electron spins have become popular because Bi has a large nuclear spin which gives rise to clock transitions (first-order insensitive to magnetic field noise). At every clock transition there are two nearly degenerate transitions between four distinct states which can be used as a pair of qubits. Here it is experimentally demonstrated that these transitions are excited by microwaves of opposite helicity such that they can be selectively driven by varying microwave polarization. This work uses a combination of a superconducting coplanar waveguide (CPW) microresonator and a dielectric resonator to flexibly generate arbitrary elliptical polarizations while retaining the high sensitivity of the CPW.

  10. The influence of ligand conformation on the thermal spin transitions in iron(III) saltrien complexes.

    Science.gov (United States)

    Pritchard, Ruth; Barrett, Simon A; Kilner, Colin A; Halcrow, Malcolm A

    2008-06-28

    We report the syntheses of six new salts of the iron(III) complexes of four hexadentate Schiff bases of the saltrien-type derived from 1,8-diamino-3,6-diazaoctane and 2 equiv. of the appropriate salicylaldehyde derivative. Three of these new compounds undergo gradual spin-transitions centred between 155-204 K in the solid state, that proceed to 35-50% completeness. One of the other compounds remains high-spin on cooling, another is low-spin, while the last undergoes spin-crossover centred above room temperature. This spin-state variability is typical of solid compounds of this type. As an aid to understanding this behaviour, the crystal structures and magnetochemistry of the known spin-crossover salts [Fe(saltrien)]PF6, [Fe(saltrien)]ClO4 and [Fe(saltrien)]BPh4 have also been reexamined. The structural chemistry of all three salts was found to differ significantly from what has been previously reported. Correlation of the crystal structures and magnetic behaviour of the compounds in this and previous work suggests that the disposition of the two ligand phenoxy groups plays an important role in determining whether high-spin [Fe(saltrien)]+ complexes can undergo thermal spin-transitions.

  11. Generalized polaron ansatz for the ground state of the sub-Ohmic spin-boson model: an analytic theory of the localization transition.

    Science.gov (United States)

    Chin, Alex W; Prior, Javier; Huelga, Susana F; Plenio, Martin B

    2011-10-14

    The sub-Ohmic spin-boson model possesses a quantum phase transition at zero temperature between a localized and a delocalized phase, whose properties have so far only been extracted by numerical approaches. Here we present an extension of the Silbey-Harris variational polaron ansatz which allows us to develop an analytical theory which correctly describes a continuous transition with mean-field exponents for 0changing correlations between the system and bath which suppress the spin coherence and drive the transition.

  12. Spin-Orbit Coupling, Quantum Dots, and Qubits in Monolayer Transition Metal Dichalcogenides

    Directory of Open Access Journals (Sweden)

    Andor Kormányos

    2014-03-01

    Full Text Available We derive an effective Hamiltonian that describes the dynamics of electrons in the conduction band of monolayer transition metal dichalcogenides (TMDC in the presence of perpendicular electric and magnetic fields. We discuss in detail both the intrinsic and the Bychkov-Rashba spin-orbit coupling induced by an external electric field. We point out interesting differences in the spin-split conduction band between different TMDC compounds. An important consequence of the strong intrinsic spin-orbit coupling is an effective out-of-plane g factor for the electrons that differs from the free-electron g factor g≃2. We identify a new term in the Hamiltonian of the Bychkov-Rashba spin-orbit coupling that does not exist in III-V semiconductors. Using first-principles calculations, we give estimates of the various parameters appearing in the theory. Finally, we consider quantum dots formed in TMDC materials and derive an effective Hamiltonian that allows us to calculate the magnetic field dependence of the bound states in the quantum dots. We find that all states are both valley and spin split, which suggests that these quantum dots could be used as valley-spin filters. We explore the possibility of using spin and valley states in TMDCs as quantum bits, and conclude that, due to the relatively strong intrinsic spin-orbit splitting in the conduction band, the most realistic option appears to be a combined spin-valley (Kramers qubit at low magnetic fields.

  13. Reentrant transitions of a mixed-spin Ising model on the diced lattice

    Directory of Open Access Journals (Sweden)

    M.Jascur

    2005-01-01

    Full Text Available Magnetic behaviour of a mixed spin-1/2 and spin-1 Ising model on the diced lattice is studied using an exact star-triangle mapping transformation. It is found that the uniaxial as well as biaxial single-ion anisotropy acting on the spin-1 sites may potentially cause a reentrant transition with two consecutive critical points. Contrary to this, the effect of next-nearest-neighbour interaction between the spin-1/2 sites possibly leads to a reentrant transition with three critical temperatures in addition to the one with two critical points only. The shape of the total magnetization versus temperature dependence is particularly investigated for the case of ferrimagnetically ordered system.

  14. Spin-Peierls transition in TiOCl

    Czech Academy of Sciences Publication Activity Database

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

    2005-01-01

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

  15. Continuous quantum phase transitions in the one-dimensional spin ...

    Indian Academy of Sciences (India)

    E-mail: adegoke@rushpost.com; adegoke@daad-alumni.de. MS received 25 January 2009; accepted 24 September 2009. Abstract. We have investigated the one-dimensional spin-1/2 axial next-nearest- neighbour Ising (ANNNI) model in two orthogonal magnetic fields at zero temperature. There are four different possible ...

  16. Sound dispersion in a spin-1 Ising system near the second-order phase transition point

    Energy Technology Data Exchange (ETDEWEB)

    Erdem, Ryza; Keskin, Mustafa

    2003-04-07

    Sound dispersion relation is derived for a spin-1 Ising system and its behaviour near the second-order phase transition point or the critical point is analyzed. The method used is a combination of molecular field approximation and Onsager theory of irreversible thermodynamics. If we assume a linear coupling of sound wave with the order parameter fluctuations in the system, we find that the dispersion which is the relative sound velocity change with frequency behaves as {omega}{sup 0}{epsilon}{sup 0}, where {omega} is the sound frequency and {epsilon} the temperature distance from the critical point. In the ordered region, one also observes a frequency-dependent velocity or dispersion minimum which is shifted from the corresponding attenuation maxima. These phenomena are in good agreement with the calculations of sound velocity in other magnetic systems such as magnetic metals, magnetic insulators, and magnetic semiconductors.

  17. Sound dispersion in a spin-1 Ising system near the second-order phase transition point

    Science.gov (United States)

    Erdem, Rýza; Keskin, Mustafa

    2003-04-01

    Sound dispersion relation is derived for a spin-1 Ising system and its behaviour near the second-order phase transition point or the critical point is analyzed. The method used is a combination of molecular field approximation and Onsager theory of irreversible thermodynamics. If we assume a linear coupling of sound wave with the order parameter fluctuations in the system, we find that the dispersion which is the relative sound velocity change with frequency behaves as ω0ε0, where ω is the sound frequency and ε the temperature distance from the critical point. In the ordered region, one also observes a frequency-dependent velocity or dispersion minimum which is shifted from the corresponding attenuation maxima. These phenomena are in good agreement with the calculations of sound velocity in other magnetic systems such as magnetic metals, magnetic insulators, and magnetic semiconductors.

  18. Novel Field-Induced Transitions Found in spin Systems on Pyrochlore Lattices

    OpenAIRE

    植田, 浩明

    2011-01-01

    We have investigated magnetic properties of two series of spin systems on pyrochlore lattices, chromium spinels and pyrochlore fluorides with 3d transition metal ions. For chromium spinels, we found novel field-induced magnetic phases with three-up and one-down spin arrangement. This type of magnetic structures are stabilized with a help of lattice distortions. Similar field-induced phase is found in a pyrochlore fluoride

  19. Electrical manipulation of spin states in a single electrostatically gated transition-metal complex

    DEFF Research Database (Denmark)

    Osorio, Edgar A; Moth-Poulsen, Kasper; van der Zant, Herre S J

    2010-01-01

    We demonstrate an electrically controlled high-spin (S = 5/2) to low-spin (S = 1/2) transition in a three-terminal device incorporating a single Mn(2+) ion coordinated by two terpyridine ligands. By adjusting the gate-voltage we reduce the terpyridine moiety and thereby strengthen the ligand-fiel...... a strongly gate-dependent singlet-triplet splitting on the low-spin side. The measured bias-spectroscopy is shown to be consistent with an exact diagonalization of the Mn-complex, and an interpretation of the data is given in terms of a simplified effective model....

  20. Theoretical study of spin-state transition in LaCoO{sub 3} using LDA+MLFT

    Energy Technology Data Exchange (ETDEWEB)

    Gorelov, Evgeny [European XFEL GmbH, Hamburg (Germany); Krivenko, Igor [University of Hamburg (Germany); Karolak, Michael [University of Wuerzburg (Germany); Lichtenstein, Alexander [European XFEL GmbH, Hamburg (Germany); University of Hamburg (Germany)

    2016-07-01

    LaCoO{sub 3} demonstrates variety of phase transitions due to competing interactions governing it's electronic structure, including metal-to-insulator transition around T∼500 K and gradual spin-state transition around T∼80-120 K. In this work we focus on spin-state transition, and use theoretical approach of M. Haverkort, taking into account transition metal ion and it's octahedral oxygen surrounding. This approach allow us to calculate the resonant Co L{sub 2,3} X-ray absorption spectra (XAS), using ab-initio calculated model parameters, i.e. nearest neighbors hopping matrix. The calculations are performed for experimental crystal structures for different temperatures in the range of 5-600 K. In our calculations we include Co 3d orbitals with full Coulomb vertex, and five ligand orbitals, constructed from 2p orbitals of O atoms, forming the octahedra around Co ion. We discuss changes in the XAS spectra induced by thermal expansion of the lattice, as well as caused by change of electron temperature.

  1. Nuclear inelastic scattering study of a dinuclear iron(II) complex showing a direct spin transition

    Energy Technology Data Exchange (ETDEWEB)

    Wolny, J. A., E-mail: wolny@physik.uni-kl.de [University of Kaiserslautern, Department of Physics (Germany); Garcia, Y. [Université Catholique de Louvain, Institute of Condensed Matter and Nanosciences, Molecules, Solids and Reactivity (IMCN/MOST) (Belgium); Faus, I.; Rackwitz, S. [University of Kaiserslautern, Department of Physics (Germany); Schlage, K.; Wille, H.-C. [DESY (Germany); Schünemann, V. [University of Kaiserslautern, Department of Physics (Germany)

    2016-12-15

    The results of the nuclear inelastic scattering (NIS)/nuclear resonance vibrational spectroscopy (NRVS) for the powder spectra of dimeric [Fe {sub 2}L{sub 5}(NCS) {sub 4}] (L = N-salicylidene-4-amino-1,2,4-triazole) complex are presented. This system is spin crossover (SCO) material tagged with a fluorophore that can sense or “feel” the SCO signal ripping through the molecular network and thereby providing an opportunity to register the SCO transition. The spectra have been measured for the low-spin and high-spin phases of the complex. The high-spin isomer reveals one broad band above 200 cm {sup −1}, while the low-spin one displays two intense bands in the range from 390 to 430 cm {sup −1}, accompanied by a number of weaker bands below this area and one at ca. 490 cm {sup −1}. A normal coordinate analysis based on density functional calculations yields the assignment of the spin marker bands to particular molecular modes. In addition the vibrational contribution to the spin transition has been estimated.

  2. Spin-flip transitions in self-assembled quantum dots

    Science.gov (United States)

    Stavrou, V. N.

    2017-12-01

    Detailed realistic calculations of the spin-flip time (T 1) for an electron in a self-assembled quantum dot (SAQD) due to emission of an acoustic phonon, using only bulk properties with no fitting parameters, are presented. Ellipsoidal lens shaped Inx Ga1-x As quantum dots, with electronic states calculated using 8-band strain dependent {k \\cdot p} theory, are considered. The phonons are treated as bulk acoustic phonons coupled to the electron by both deformation potential and piezoelectric interactions. The dependence of T 1 on the geometry of SAQD, on the applied external magnetic field and on the lattice temperature is highlighted. The theoretical results are close to the experimental measurements on the spin-flip times for a single electron in QD.

  3. Cascade of magnetic field induced spin transitions in LaCoO3.

    Science.gov (United States)

    Altarawneh, M M; Chern, G-W; Harrison, N; Batista, C D; Uchida, A; Jaime, M; Rickel, D G; Crooker, S A; Mielke, C H; Betts, J B; Mitchell, J F; Hoch, M J R

    2012-07-20

    We present magnetization and magnetostriction studies of LaCoO3 in magnetic fields approaching 100 T. In contrast with expectations from single-ion models, the data reveal two distinct first-order transitions and well-defined magnetization plateaus. The magnetization at the higher plateau is only about half the saturation value expected for spin-1 Co3+ ions. These findings strongly suggest collective behavior induced by interactions between different electronic configurations of Co3+ ions. We propose a model that predicts crystalline spin textures and a cascade of four magnetic phase transitions at high fields, of which the first two account for the experimental data.

  4. 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....

  5. Light-induced transition in spin-crossover compounds with correlated stochastic processes

    Science.gov (United States)

    Gudyma, Iurii V.; Maksymov, Artur

    2015-11-01

    The stochastic kinetics of a photoinduced phase transition in spin-crossover compounds in the presence of environmental background and systems internal noises were studied. The correlation phenomena that determine the color of internal and external noises was taken into account. The mathematical framework for the study of light-induced transition in spin-crossover nanoparticles was based on the Langevin equation and steady solution of corresponding Fokker-Planck equation. The system behavior was described by nonequilibrium (dynamic) potential in terms of Lyapunov functions for the deterministic case and by stochastic Fokker-Planck potential in the noise case action.

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

    Science.gov (United States)

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

    2015-08-17

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

  7. Quantum spin liquids and the metal-insulator transition in doped semiconductors.

    Science.gov (United States)

    Potter, Andrew C; Barkeshli, Maissam; McGreevy, John; Senthil, T

    2012-08-17

    We describe a new possible route to the metal-insulator transition in doped semiconductors such as Si:P or Si:B. We explore the possibility that the loss of metallic transport occurs through Mott localization of electrons into a quantum spin liquid state with diffusive charge neutral "spinon" excitations. Such a quantum spin liquid state can appear as an intermediate phase between the metal and the Anderson-Mott insulator. An immediate testable consequence is the presence of metallic thermal conductivity at low temperature in the electrical insulator near the metal-insulator transition. Further, we show that though the transition is second order, the zero temperature residual electrical conductivity will jump as the transition is approached from the metallic side. However, the electrical conductivity will have a nonmonotonic temperature dependence that may complicate the extrapolation to zero temperature. Signatures in other experiments and some comparisons with existing data are made.

  8. The Academic Spin-Offs as an Engine of Economic Transition in Eastern Europe. A Path-Dependent Approach

    Science.gov (United States)

    Tchalakov, Ivan; Mitev, Tihomir; Petrov, Venelin

    2010-01-01

    The paper questions some of the premises in studying academic spin-offs in developed countries, claiming that when taken as characteristics of "academic spin-offs per se," they are of little help in understanding the phenomenon in the Eastern European countries during the transitional and post-transitional periods after 1989. It argues…

  9. Scaling of quantum Fisher information close to the quantum phase transition in the XY spin chain

    Energy Technology Data Exchange (ETDEWEB)

    Ye, En-Jia, E-mail: yeenjia@jiangnan.edu.cn [Jiangsu Provincial Research Center of Light Industrial Optoelectronic Engineering and Technology, School of Science, Jiangnan University, Wuxi 214122 (China); Hu, Zheng-Da [Jiangsu Provincial Research Center of Light Industrial Optoelectronic Engineering and Technology, School of Science, Jiangnan University, Wuxi 214122 (China); Wu, Wei [Zhejiang Institute of Modern Physics and Physics Department, Zhejiang University, Hangzhou 310027 (China)

    2016-12-01

    The quantum phase transition of an XY spin chain is investigated by employing the quantum Fisher information encoded in the ground state. It is shown that the quantum Fisher information is an effective tool for characterizing the quantum criticality. The quantum Fisher information, its first and second derivatives versus the transverse field display the phenomena of sudden transition, sudden jump and divergence, respectively. Besides, the analysis of finite size scaling for the second derivative of quantum Fisher information is performed.

  10. Spin induced ferroelectric-like structural transition in a metal

    Science.gov (United States)

    Guo, Yanfeng; Feng, Hai; Andrew, Princep; Manuel, Pascal; Yamaura, Kazunari; Andrew, Boothroyd

    2015-03-01

    LiOsO3 represents a previously only known example of ``ferroelectric metal,'' a concept presented by Anderson and Blount in 1965, with the properties being promoted by electron lattice coupling involving Li+ ions displacement in the crystal structure [Y. Shi et al., Nat. Mater. 12, 1024(2013)]. We report that in Pb2CoOsO6, a new ordered double-perovskite with a centrosymmetric monoclinic space group of P21/n, a ferroelectric-like structural transition occurs at ~ 38 K in the metallic state, i.e. a continuous second order transition to a noncentrosymmetric structure (space group: P1) associated by appearance of a nominal unique polar axis along the c-axis. The phase transition is coincident with a magnetic transition at the same temperature which corresponds to a long-range antiferromagnetic order. The magnetic structure analysis and theoretical calculations prove that the antiferromagnetic ordering is the driven force for the structural transition in Pb2CoOsO6 and it represents the first double-perovskite ``ferroelectric metal'' involving a magnetic ordering. United Kingdom Engineering and Physical Sciences Research Council (EPSRC).

  11. Spin transition in [Fe(phen){sub 2}(NCS){sub 2}] - {mu}SR study

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Y.; Boland, Y. [Unite de Chimie des Materiaux Inorganiques et Organiques, Departement de Chimie, Faculte des Sciences, Universite catholique de Louvain, Place Louis Pasteur 1, 1348 Louvain-la-Neuve (Belgium); Ksenofontov, V.; Guetlich, P. [Institut fuer Anorganische Chemie und Analytische Chemie, Universitaet Mainz, 55099 Mainz (Germany); Campbell, S.J. [School of Physical, Environmental and Mathematical Sciences, The University of New South Wales, Australian Defence Force Academy, Canberra, ACT 2600 (Australia); Lord, J.S. [ISIS, Rutherford Appleton Laboratory, Chilton, Didcot, OX11 OQX (United Kingdom)

    2004-12-01

    The reversible thermal spin transition which occurs in [Fe(phen){sub 2}(NCS){sub 2}] around T{sub 1/2} {proportional_to} 177 K has been investigated by muon spin relaxation ({mu}SR) ({proportional_to}10-280 K). The depolarisation curves are well described by two Lorentzian lines represent fast and slow components in the decay curves, with the initial asymmetry parameter of the fast component found to track the spin transition in [Fe(phen){sub 2}(NCS){sub 2}]. Comparison of zero-field and transverse field (20 Oe) {mu}SR measurements shows that diamagnetic muonic species occur over the entire temperature range. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Spin-glass and antiferromagnetic transitions in Ru2-xFexCrSi

    Science.gov (United States)

    Hiroi, Masahiko; Ko, Haku; Nakashima, Shingo; Shigeta, Iduru; Ito, Masakazu; Manaka, Hirotaka; Terada, Norio

    2012-12-01

    In this study the properties of the Heusler compounds Ru2-xFexCrSi (0CrSi was revealed to exhibit two anomalies in the temperature dependence of magnetization M(T); one is a peak in M(T) at T*N ~ 30 K and the other is strong irreversibility in M(T) below T*N, the onset of which is defined as Tg. M(T) and specific heat CP(T) of Ru2CrSi are measured. A clear peak is observed in both M(T) and CP(T). This is in quite contrast to the case for Ru1.9Fe0.1CrSi, where no anomaly in CP(T) was observed at T*N or at any other temperatures. These indicate that an antiferromagnetic transition occurs at TN = 14 K in Ru2CrSi. For x = 0.02 the characteristic two anomalies in M(T) are also found at various magnetic fields, and their field dependence is basically the same as that for x = 0.1. These two anomalies are suggestive of successive spin-glass transitions. As for the dependence of the two anomalies on x, Tg does not change with x, whereas T*N decreases with decreasing x and seems to approach Tg at zero field.

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

    Czech Academy of Sciences Publication Activity Database

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

    2005-01-01

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

  14. A continuous Mott transition between a metal and a quantum spin liquid

    Science.gov (United States)

    Mishmash, Ryan V.; Gonzalez, Ivan; Melko, Roger G.; Motrunich, Olexei I.; Fisher, Matthew P. A.

    2015-03-01

    More than half a century after first being proposed by Sir Nevill Mott, the deceptively simple question of whether the interaction-driven electronic metal-insulator transition may be continuous remains enigmatic. Recent experiments on two-dimensional materials suggest that when the insulator is a quantum spin liquid, lack of magnetic long-range order on the insulating side may cause the transition to be continuous, or only very weakly first order. Motivated by this, we study a half-filled extended Hubbard model on a triangular lattice strip geometry. We argue, through use of large-scale numerical simulations and analytical bosonization, that this model harbors a continuous (Kosterlitz-Thouless-like) quantum phase transition between a metal and a gapless spin liquid characterized by a spinon Fermi sea, i.e., a ``spin Bose metal''. These results may provide a rare insight into the development of Mott criticality in strongly interacting two-dimensional materials and elucidate a mechanism by which spin-liquid phases are stabilized in the vicinity of such transitions.

  15. Direct measurement of the low temperature spin state transitions in La1-xSrxCoO3 (0.05 < x < 0.3)

    Science.gov (United States)

    Gulec, A.; Klie, R. F.

    2014-12-01

    Sr-doped LaCoO3 has a complex magnetic phase diagram, which is believed to be directly correlated to changes in the crystal structure and ordering of the Co3+ spin states. In this work, we study the low temperature Co3+-ion spin state transitions in Sr-doped LaCoO3 around the critical doping concentration where a metal to insulator transition has been observed using electron energy-loss spectroscopy of the O K-edge combined with the Co L-edge fine structure. We measure the local spin state of the Co3+-ions and we demonstrate that the Co3+ spin-state transition only occurs in La0.95Sr0.05CoO3 single-crystal materials in the temperature range accessible by LN2 in-situ cooling, while no structural symmetry change is observed. The presence of this low-temperature spin-state transition in La1-xSrxCoO3 (x LaCoO3.

  16. Quantum phase transition of a magnet in a spin bath

    DEFF Research Database (Denmark)

    Rønnow, H.M.; Parthasarathy, R.; Jensen, J.

    2005-01-01

    The excitation spectrum of a model magnetic system, LiHoF(4), was studied with the use of neutron spectroscopy as the system was tuned to its quantum critical point by an applied magnetic field. The electronic mode softening expected for a quantum phase transition was forestalled by hyperfine...

  17. Spin, Charge, and Bonding in Transition Metal Mono Silicides

    NARCIS (Netherlands)

    Marel, D. van der; Damascelli, A.; Schulte, K.; Menovsky, A. A.

    1997-01-01

    Published in: Physica B 244 (1998) 138-147 citations recorded in [Science Citation Index] Abstract: We review some of the relevant physical properties of the transition metal mono-silicides with the FeSi structure (CrSi, MnSi, FeSi, CoSi, NiSi, etc) and explore the relation between their structural

  18. Unexpected Spin-Crossover and a Low-Pressure Phase Change in an Iron(II)/Dipyrazolylpyridine Complex Exhibiting a High-Spin Jahn-Teller Distortion.

    Science.gov (United States)

    Kershaw Cook, Laurence J; Thorp-Greenwood, Flora L; Comyn, Tim P; Cespedes, Oscar; Chastanet, Guillaume; Halcrow, Malcolm A

    2015-07-06

    The synthesis of 4-methyl-2,6-di(pyrazol-1-yl)pyridine (L) and four salts of [FeL2]X2 (X(-) = BF4(-), 1; X(-) = ClO4(-), 2; X(-) = PF6(-), 3; X(-) = CF3SO3(-), 4) are reported. Powder samples of 1 and 2 both exhibit abrupt, hysteretic spin-state transitions on cooling, with T1/2↓ = 204 and T1/2↑ = 209 K (1), and T1/2↓ = 175 and T1/2↑ = 193 K (2). The 18 K thermal hysteresis loop for 2 is unusually wide for a complex of this type. Single crystal structures of 2 show it to exhibit a Jahn-Teller-distorted six-coordinate geometry in its high-spin state, which would normally inhibit spin-crossover. Bulk samples of 1 and 2 are isostructural by X-ray powder diffraction, and undergo a crystallographic phase change during their spin-transitions. At temperatures below T1/2, exposing both compounds to 10(-5) Torr pressure inside the powder diffractometer causes a reversible transformation back to the high-temperature crystal phase. Consideration of thermodynamic data implies this cannot be accompanied by a low → high spin-state change, however. Both compounds also exhibit the LIESST effect, with 2 exhibiting an unusually high T(LIESST) of 112 K. The salts 3 and 4 are respectively high-spin and low-spin between 3 and 300 K, with crystalline 3 exhibiting a more pronounced version of the same Jahn-Teller distortion.

  19. The Influence of the Perovskite-post Perovskite Phase Transition and the Spin Transition in Iron on Layered Mantle Convection

    Science.gov (United States)

    Shahnas, H.; Peltier, W.

    2008-12-01

    The interaction between the endothermic phase transition(s) at the base of the transition zone and both subducting lithosphere and uprising plumes originating from the deep mantle remains a key issue in geodynamics. The rates of both heat and mass transfer between the upper and the lower mantle are controlled by this interaction. Factors that govern its impact include not only the Clapeyron slope of the transition but also the contrast in physical properties across the interface, notably viscosity. Mass transfer across the level of the endothermic transition at 660 km depth is inhibited by a viscosity increase. Evidence for such inhibition derives from several lines of argument. For example, seismic tomographic images of downgoing slabs trapped in the transition region above 660 km depth are common. We will describe a sequence of new simulations of convective mixing which include the most accurate representations of the temperature and pressure dependence of thermal conductivity, thermal expansively and viscosity as well as the presence of the near surface exothermic and endothermic traditional phase transitions that bracket the transition zone as well as the Perovskite-post Perovskite (Pv-pPv) deep mantle transition that appears to define the D" layer. In these new models we investigate the influence Pv-pPv transition and the spin transition in iron on mantle dynamics, with a focus upon the permeability to mass transfer of the 660 phase transition. This endothermic transition operating in conjunction with a modest but abrupt viscosity increase at 660 km depth results in an episodic but significant decrease in the radial mass flux. The frequency of mantle avalanches decreases as the viscosity contrast increases and the mass flux in each avalanche becomes more diffuse and less intense.

  20. Spin and orbital contributions to collective M1 transitions in /sup 46,48/Ti

    Energy Technology Data Exchange (ETDEWEB)

    Nojarov, R.; Faessler, A.; Civitarese, O.

    1987-01-08

    Low- and high-lying K/sup ..pi../=1/sup +/ states and M1 transitions in /sup 46,48/Ti are studied. The model hamiltonian is treated in the quasi-particle random phase approximation (QRPA) with an exact restoration of its rotational invariance. A considerable spin contribution to the transition matrix elements is found for the low-energy (about 4 MeV) strong M1 transition (the orbital contribution being 30-70% of the spin one), although the microscopic structure of this state in /sup 46/Ti is typical for an orbital isovector excitation. The calculated energies and B(M1) values are in a good agreement with the experimental data. The results are compared to the estimates of the isovector scissor model.

  1. Hindered spin-transitions in the dissociative adsorption of O{sub 2} on Al(111)

    Energy Technology Data Exchange (ETDEWEB)

    Carbogno, Christian; Gross, Axel [Inst. of Theoretical Chemistry, University of Ulm (Germany); Behler, Joerg [Dept. of Chemistry and Applied Biosciences, ETH Zuerich (Switzerland); Reuter, Karsten [Fritz-Haber-Institut der Max- Planck-Gesellschaft, Berlin (Germany)

    2007-07-01

    The low stick ing probability for thermal O{sub 2} molecules at Al(111) has (DE) recently been related to spin selection rules, which hinder a spin transition from the initial O{sub 2} gas-phase triplet state to the singlet state of the adsorbed O atoms. A constrained density-functional theory (DFT) approach was employed to compute the potential energy surfaces (PESs) of O{sub 2} in different spin-configurations, and the lowered sticking probability was calculated when restricting the O{sub 2} molecule to motion on the spin-triplet PES only. Here, we extend these studies by considering the dissociation dynamics on multiple spin PESs, allowing transitions between them within the quantum-classical fewestswitch algorithm as recently implemented, and calculating the nonadiabatic coupling between the PESs with various quantum chemical methods. The established framework enables us to study the adsorption process in detail, both as a function of the incident kinetic energy and incidence angle. Obtaining good agreement with experiment, we critically discuss the effects of the approximate non-adiabatic couplings and the uncertainties underlying the DFT PESs.

  2. Direct measurement of the low-temperature spin-state transition in LaCoO3.

    Science.gov (United States)

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

    2007-07-27

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

  3. Picture change error in quasirelativistic electron/spin density, Laplacian and bond critical points

    Energy Technology Data Exchange (ETDEWEB)

    Bučinský, Lukáš, E-mail: lukas.bucinsky@stuba.sk [Slovak University of Technology, FCHPT, Institute of Physical Chemistry and Chemical Physics, Radlinskeho 9, Bratislava SK-812 37 (Slovakia); Kucková, Lenka; Malček, Michal; Kožíšek, Jozef; Biskupič, Stanislav [Slovak University of Technology, FCHPT, Institute of Physical Chemistry and Chemical Physics, Radlinskeho 9, Bratislava SK-812 37 (Slovakia); Jayatilaka, Dylan [University of Western Australia, Department of Chemistry, 35 Stirling Hwy, Crawley, WA 6009 (Australia); Büchel, Gabriel E. [University of Vienna, Institute of Inorganic Chemistry, Währinger Str. 42, A-1090 Vienna (Austria); King Abdullah University of Science and Technology, Division for Physical Sciences and Engineering and KAUST Catalysis Center, Thuwal (Saudi Arabia); Arion, Vladimir B. [University of Vienna, Institute of Inorganic Chemistry, Währinger Str. 42, A-1090 Vienna (Austria)

    2014-06-25

    Highlights: • Quasirelativistic study of electron density topology of Os and Ru complexes. • Electron/spin densities and negative Laplacian of electron density presented. • Analytic correction of picture change error at IOTC level. • Relativistic and spin–orbit effects are considered, IOTC vs. DKH2 compared. - Abstract: The change of picture of the quasirelativistic Hartree–Fock wave functions is considered for electron/spin densities, the negative Laplacian of electron density and the appropriate bond critical point characteristics from the Quantum Theory of Atoms In Molecules (QTAIM). [OsCl{sub 5}(Hpz)]{sup −} and [RuCl{sub 5}(NO)]{sup 2−} transition metal complexes are considered. Both, scalar relativistic and spin–orbit effects have been accounted for using the Infinite Order Two Component (IOTC) Hamiltonian. Picture change error (PCE) correction in the electron and spin densities and the Laplacian of electron density are treated analytically. Generally, PCE is found significant only in the core region of the atoms for the electron/spin density as well as Laplacian.

  4. Exploiting pressure to induce a "guest-blocked" spin transition in a framework material

    Energy Technology Data Exchange (ETDEWEB)

    Sciortino, Natasha F.; Ragon, Florence; Zenere, Katrina A.; Southon, Peter D.; Halder, Gregory J.; Chapman, Karena W.; Pineiro-Lopez, Lucia; Real, Jose A.; Kepert, Cameron J.; Neville, Suzanne M.

    2016-10-17

    A new functionalized 1,2,4-trizole ligand 4-[(E)-2-(5-methyl-2-thienyl)vinyl]-1,2,4-triazole (thiome) was prepared to assess the structural and magnetic consequence of ligand steric bulk in the resultant framework material [FeIIPd(CN)4(thiome)2]·2(H2O) (A·2(H2O)). Structural studies reveal that the pore size is smaller than realted 2-D Hofmann-type materials and that the water molecules can be reversibly removed with retention of the porous host framework. Magnetic measurements show ‘on-off’ sensing to the presence of water. The hydrated phase is spin crossover (SCO) inactive whereas the dehydrated phase undergoes an abrupt and hysteretic one-step spin transition. Partial dehydration (A·n(H2O), 0 ≤ n ≤ 2) leads to systematically varying spin transition temperatures further demonstrating qualitative sensing. These studies suggest that the SCO properties are governed by internal lattice pressure effects. Variable pressure structure and magnetic studies on the hydrated phase, A·2(H2O), reveal that such internal guest pressure effects can be overcome with moderate external pressure application (0 – 0.68 GPa) resulting in a two-step spin transition at ambient temperatures at 0.68 GPa.

  5. Coupled spin-valley-dynamics in singe-layer transition metal dichalcogenides

    Science.gov (United States)

    Plechinger, Gerd; Nagler, Philipp; Schüller, Christian; Korn, Tobias

    Single layers of transition metal dichalcogenides (TMDCs) like MoS2 and WS2 can be produced by simple mechanical exfoliation. Offering a direct bandgap at the K-points in the Brillouin zone, they represent a promising semiconductor material for flexible and transparent optoelectronic applications. Due to inversion symmetry breaking together with strong spin-orbit-interaction, the valley and spin degrees of freedom are coupled in monolayer TMDCs. Via circularly polarized optical excitation, an efficient polarization of the K+ or the K- valley can be generated. Here, we investigate the dynamics of these coupled spin-valley polarizations in monolayer MoS2 and WS2 by means of photoluminescence spectroscopy and time-resolved Kerr rotation (TRKR). The results indicate a maximum achievable spin-valley-lifetime in these materials exceeding one nanosecond at low temperatures. Furthermore, we extract the dependence of the spin-valley lifetime on temperature. By varying the excitation energy, we reveal the excitonic resonances as well as the spin-polarized bandstructure around the K valleys common to monolayer TMDCs.

  6. Quantum phase transitions in effective spin-ladder models for graphene zigzag nanoribbons

    Science.gov (United States)

    Koop, Cornelie; Wessel, Stefan

    2017-10-01

    We examine the magnetic correlations in quantum spin models that were derived recently as effective low-energy theories for electronic correlation effects on the edge states of graphene nanoribbons. For this purpose, we employ quantum Monte Carlo simulations to access the large-distance properties, accounting for quantum fluctuations beyond mean-field-theory approaches to edge magnetism. For certain chiral nanoribbons, antiferromagnetic interedge couplings were previously found to induce a gapped quantum disordered ground state of the effective spin model. We find that the extended nature of the intraedge couplings in the effective spin model for zigzag nanoribbons leads to a quantum phase transition at a large, finite value of the interedge coupling. This quantum critical point separates the quantum disordered region from a gapless phase of stable edge magnetism at weak intraedge coupling, which includes the ground states of spin-ladder models for wide zigzag nanoribbons. To study the quantum critical behavior, the effective spin model can be related to a model of two antiferromagnetically coupled Haldane-Shastry spin-half chains with long-ranged ferromagnetic intrachain couplings. The results for the critical exponents are compared also to several recent renormalization-group calculations for related long-ranged interacting quantum systems.

  7. Unambiguously identifying spin states of transition-metal ions in the Earth (Invited)

    Science.gov (United States)

    Hsu, H.

    2010-12-01

    The spin state of a transition-metal ion in crystalline solids, defined by the number of unpaired electrons in the ion’s incomplete 3d shell, may vary with many factors, such as temperature, pressure, strain, and the local atomic configuration, to name a few. Such a phenomenon, known as spin-state crossover, plays a crucial role in spintronic materials. Recently, the pressure-induced spin-state crossover in iron-bearing minerals has been recognized to affect the minerals’ structural and elastic properties. However, the detailed mechanism of such crossover in iron-bearing magnesium silicate perovskite, the most abundant mineral in the Earth, remains unclear. A significant part of this confusion arises from the difficulty in reliably extracting the spin state from experiments. For the same reason, the thermally-induced spin-state crossover in lanthanum cobaltite (LaCoO3) has been controversial for more than four decades. In this talk, I will discuss how first-principle calculations can help clarifying these long-standing controversies. In addition to the total energy, equation of state, and elastic properties of each spin state, first-principle calculations also predict the electric field gradient (EFG) at the nucleus of each transition-metal ion. Our calculations showed that the nuclear EFG, a quantity that can be measured via Mössbauer or nuclear magnetic resonance (NMR) spectroscopy, depends primarily on the spin state, irrespective of the concentration or configuration of transition-metal ions. Such robustness makes EFG a unique fingerprint to identify the spin state. The combination of first-principle calculations and Mössbauer/NMR spectroscopy can therefore be a reliable and efficient approach in tackling spin-state crossover problems in the Earth. This work was primarily supported by the MRSEC Program of NSF under Awards Number DMR-0212302 and DMR-0819885, and partially supported by NSF under ATM-0428774 (V-Lab), EAR-1019853, and EAR-0810272. The

  8. Phase transitions of Ising mixed spin 1 and 3/2 with random crystal field distribution

    Science.gov (United States)

    Sabri, S.; EL Falaki, M.; EL Yadari, M.; Benyoussef, A.; EL Kenz, A.

    2016-10-01

    The thermal and magnetic properties of the mixed spin-1 and spin-3/2 in the presence of the random crystal field are studied within the mean field approach based on the Bogoliubov inequality for the Gibbs free energy. The model exhibits first, second order transitions, a tricritical point, triple point and an isolated critical end point. It is found that the system displays simple and double compensation temperatures, five topologies of the phase diagrams. A re-entrant phenomenon is also discussed and the thermal dependences of total magnetization according to extended Neel classification have been also given.

  9. Large spin splitting in the conduction band of transition metal dichalcogenide monolayers

    OpenAIRE

    Kósmider, K.; González, Jhon W.; Fernández Rossier, Joaquín

    2013-01-01

    We study the conduction band spin splitting that arises in transition metal dichalcogenide (TMD) semiconductor monolayers such as MoS2, MoSe2, WS2, and WSe2 due to the combination of spin-orbit coupling and lack of inversion symmetry. Two types of calculation are done. First, density functional theory (DFT) calculations based on plane waves that yield large splittings, between 3 and 30 meV. Second, we derive a tight-binding model that permits to address the atomic origin of the splitting. The...

  10. Analytic model for low energy excitation states and phase transitions in spin-ice systems

    Science.gov (United States)

    López-Bara, F. I.; López-Aguilar, F.

    2017-04-01

    Low energy excitation states in magnetic structures of the so-called spin-ices are produced via spin flips among contiguous tetrahedra of their crystal structure. These spin flips generate entities which mimic magnetic dipoles in every two tetrahedra according to the dumbbell model. When the temperature increases, the spin-flip processes are transmitted in the lattice, generating so-called Dirac strings, which constitute structural entities that can present mimetic behavior similar to that of magnetic monopoles. In recent studies of both specific heat and ac magnetic susceptibility, two (even possibly three) phases have been shown to vary the temperature. The first of these phases presents a sharp peak in the specific heat and another phase transition occurs for increasing temperature whose peak is broader than that of the former phase. The sharp peak occurs when there are no free individual magnetic charges and temperature of the second phase transition coincides with the maximum proliferation of free deconfined magnetic charges. In the present paper, we propose a model for analyzing the low energy excitation many-body states of these spin-ice systems. We give analytical formulas for the internal energy, specific heat, entropy and their temperature evolution. We study the description of the possible global states via the nature and structure of their one-body components by means of the thermodynamic functions. Below 0.37 K, the Coulomb-like magnetic charge interaction can generate a phase transition to a condensation of pole-antipole pairs, possibly having Bose-Einstein structure which is responsible for the sharp peak of the first phase transition. When there are sufficient free positive and negative charges, the system tends to behave as a magnetic plasma, which implies the broader peak in the specific heat appearing at higher temperature than the sharper experimental peak.

  11. Analytic model for low energy excitation states and phase transitions in spin-ice systems.

    Science.gov (United States)

    López-Bara, F I; López-Aguilar, F

    2017-04-20

    Low energy excitation states in magnetic structures of the so-called spin-ices are produced via spin flips among contiguous tetrahedra of their crystal structure. These spin flips generate entities which mimic magnetic dipoles in every two tetrahedra according to the dumbbell model. When the temperature increases, the spin-flip processes are transmitted in the lattice, generating so-called Dirac strings, which constitute structural entities that can present mimetic behavior similar to that of magnetic monopoles. In recent studies of both specific heat and ac magnetic susceptibility, two (even possibly three) phases have been shown to vary the temperature. The first of these phases presents a sharp peak in the specific heat and another phase transition occurs for increasing temperature whose peak is broader than that of the former phase. The sharp peak occurs when there are no free individual magnetic charges and temperature of the second phase transition coincides with the maximum proliferation of free deconfined magnetic charges. In the present paper, we propose a model for analyzing the low energy excitation many-body states of these spin-ice systems. We give analytical formulas for the internal energy, specific heat, entropy and their temperature evolution. We study the description of the possible global states via the nature and structure of their one-body components by means of the thermodynamic functions. Below 0.37 K, the Coulomb-like magnetic charge interaction can generate a phase transition to a condensation of pole-antipole pairs, possibly having Bose-Einstein structure which is responsible for the sharp peak of the first phase transition. When there are sufficient free positive and negative charges, the system tends to behave as a magnetic plasma, which implies the broader peak in the specific heat appearing at higher temperature than the sharper experimental peak.

  12. Leading change: evidence-based transition.

    Science.gov (United States)

    Lewis, Brennan; Allen, Stephanie

    2015-01-01

    The purpose of this article was to provide a framework for evidence-based transition of patient populations within an acute care pediatric institution. Transition within a hospital is foreseeable, given the ever-changing needs of the patients within an evolving healthcare system. These changes include moving patient populations because of expansion, renovation, or cohorting similar patient diagnoses to provide care across a continuum. Over the past 1 to 2 years, Children's Health Children's Medical Center Dallas has experienced a wide variety of transition. To provide a smooth transition for patients and families into new care areas resulting in a healthy work environment for all team members. The planning phase for patient population moves, and transition should address key aspects to include physical location and care flow, supplies and equipment, staffing model and human resources (HR), education and orientation, change process and integrating teams, and family preparation. It is imperative to consider these aspects in order for transitions within a healthcare system to be successful. During a time of such transitions, the clinical nurse specialist (CNS) is a highly valuable team member offering a unique perspective and methodological approach, which is central to the new initiative's overall success. The themes addressed in this article on evidence-based transition are organized according to the CNS spheres of influence: system/organization, patient/family, and nursing. An evidence-based transition plan was developed and implemented successfully with the support from the CNS for 3 patient populations. Organizational leadership gained an increased awareness of the CNS role at the conclusion of each successful transition. The CNS plays a pivotal role as clinical experts and proponents of evidence-based practice and effects change in the system/organization, nursing, and patient/family spheres of influence. While transitions can be a source of stress for leaders

  13. Pressure-induced hysteresis in the high spin {r_reversible} low spin transition in bis(2,4-bis(pyridin-2-yl)thiazole) iron(II) tetrafluoroborate

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharjee, A; Ksenofontov, V; Guetlich, P [Institut fuer Anorganische Chemie und Analytische Chemie, Johannes-Gutenberg Universitaet, D-55099 Mainz (Germany); Goodwin, H A [School of Chemistry, University of New South Wales, Sydney, NSW 2052 (Australia)], E-mail: ashis.bhattacharjee@visva-bharati.ac.in, E-mail: guetlich@uni-mainz.de

    2009-01-14

    Studies of the spin transition behavior of the mononuclear compound [Fe(pythiaz){sub 2}](BF{sub 4}){sub 2} have been carried out under hydrostatic pressures up to 9.13 kbar in the 5-300 K temperature range. Under ambient pressure this compound exhibits an approximately half-step (incomplete) HS {r_reversible} LS transition with T{sub 1/2} = 146 K without any thermal hysteresis. At pressures up to 4.5 kbar the behavior remains similar but with an upward displacement of T{sub 1/2} and a slight decrease in the residual high spin fraction at low T. Application of higher pressures resulted in an almost complete two-step spin transition with several unusual pressure effects. Along with the expected pressure dependence of T{sub 1/2} the surprising appearance of hysteresis in the spin transition curves was observed. It is suggested that the likely origin of this unprecedented behavior is a pressure-induced structural change.

  14. Pressure-induced hysteresis in the high spin [Formula: see text] low spin transition in bis(2,4-bis(pyridin-2-yl)thiazole) iron(II) tetrafluoroborate.

    Science.gov (United States)

    Bhattacharjee, A; Ksenofontov, V; Goodwin, H A; Gütlich, P

    2009-01-14

    Studies of the spin transition behavior of the mononuclear compound [Fe(pythiaz)(2)](BF(4))(2) have been carried out under hydrostatic pressures up to 9.13 kbar in the 5-300 K temperature range. Under ambient pressure this compound exhibits an approximately half-step (incomplete) HS [Formula: see text] LS transition with T(1/2) = 146 K without any thermal hysteresis. At pressures up to 4.5 kbar the behavior remains similar but with an upward displacement of T(1/2) and a slight decrease in the residual high spin fraction at low T. Application of higher pressures resulted in an almost complete two-step spin transition with several unusual pressure effects. Along with the expected pressure dependence of T(1/2) the surprising appearance of hysteresis in the spin transition curves was observed. It is suggested that the likely origin of this unprecedented behavior is a pressure-induced structural change.

  15. Thermal phase transition in artificial spin ice systems induces the formation and migration of monopole-like magnetic excitations

    Energy Technology Data Exchange (ETDEWEB)

    León, Alejandro

    2016-11-01

    Artificial spin ice systems exhibit monopole-like magnetic excitations. We develop here a theoretical study of the thermal phase transition of an artificial spin ice system, and we elucidate the role of the monopole excitations in the transition temperature. The dynamics of the spin ice is described by an efficient model based on cellular automata, which considers both thermal effects and dipolar interactions. We have established the critical temperature of the phase transition as function of the magnetic moment and the energy barrier of reversion. In addition, we predict that thermal gradients in the system induce the motion of elementary excitations, which could permit to manipulate monopole-like states.

  16. Hindered spin-transitions in the dissociative adsorption of O{sub 2} on Al(111)

    Energy Technology Data Exchange (ETDEWEB)

    Carbogno, Christian; Gross, Axel [Institut fuer Theoretische Chemie, Universitaet Ulm (Germany); Behler, Joerg [Lehrstuhl fuer Theoretische Chemie, Ruhr-Universitaet Bochum (Germany); Reuter, Karsten [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin (Germany)

    2008-07-01

    The low sticking probability for thermal O{sub 2} molecules at Al(111) has recently been related to spin selection rules, which hinder transitions from the initial O{sub 2} gas-phase triplet state to the singlet state of the adsorbed O atoms. A constrained DFT approach was employed to compute potential energy surfaces (PESs) of O{sub 2} in different spin-configurations from the surface, and the experimental sticking probability was qualitatively reproduced when restricting the O{sub 2} molecule to motion on the spin-triplet PES only. Here, we extend these studies by considering the dissociation dynamics on multiple spin PESs, allowing transitions between them within Tully's fewest-switches algorithm as recently implemented. The required non-adiabatic coupling elements have been derived in an ab initio fashion from the comparison between adiabatic and constrained-DFT PESs. Within this framework we obtain both good agreement with experiment for the fundamental features of the system as well as deeper insight into more peculiar characteristics of the dynamics. Based on our results, we propose experiments which can be used for the validation of our approach.

  17. Analytic renormalized bipartite and tripartite quantum discords with quantum phase transition in XXZ spins chain

    Science.gov (United States)

    Joya, Wajid; Khan, Salman; Khalid Khan, M.; Alam, Sher

    2017-05-01

    The behavior of bipartite quantum discord (BQD) and tripartite quantum discord (TQD) in the Heisenberg XXZ spins chain is investigated with the increasing size of the system using the approach of the quantum renormalization group method. Analytical relations for both BQD and TQD are obtained and the results are checked through numerical optimization. In the thermodynamics limit, both types of discord exhibit quantum phase transition (QPT). The boundary of QPT links the phases of saturated discord and zero discord. The first derivative of both discords becomes discontinuous at the critical point, which corresponds to the second-order phase transition. Qualitatively identical, the amount of saturated BQD strongly depends on the relative positions of spins inside a block. TQD can be a better candidate than BQD both for analyzing QPT and implementing quantum information tasks. The scaling behavior in the vicinity of the critical point is discussed.

  18. Thermal spin transition of circularly shaped nanoparticles in a core-shell structure investigated with an electroelastic model

    Science.gov (United States)

    Slimani, A.; Boukheddaden, K.; Yamashita, K.

    2014-06-01

    The functionalization of spin crossover materials as nanoscopic devices is a big challenge to overcome. It will entail a detailed exploration of why and how size reduction affects spin crossover behavior. We investigated the thermal spin transition of a nanoparticle in a core-shell structure as a function of particle size, the intensity of interactions between molecules, and also the thickness of the shell and its stiffness. The analysis was performed using an electroelastic model based on Monte Carlo methods on a distortable two-dimensional lattice, the sites of which are occupied by high-spin or low-spin atoms. Such analysis reflects the crucial influence of size as well as of the surrounding environment on the behavior of the spin transition, and it provides reliable explanations based on the elastic properties of the system.

  19. A spin transition mechanism for cooperative adsorption in metal-organic frameworks.

    Science.gov (United States)

    Reed, Douglas A; Keitz, Benjamin K; Oktawiec, Julia; Mason, Jarad A; Runčevski, Tomče; Xiao, Dianne J; Darago, Lucy E; Crocellà, Valentina; Bordiga, Silvia; Long, Jeffrey R

    2017-10-05

    Cooperative binding, whereby an initial binding event facilitates the uptake of additional substrate molecules, is common in biological systems such as haemoglobin. It was recently shown that porous solids that exhibit cooperative binding have substantial energetic benefits over traditional adsorbents, but few guidelines currently exist for the design of such materials. In principle, metal-organic frameworks that contain coordinatively unsaturated metal centres could act as both selective and cooperative adsorbents if guest binding at one site were to trigger an electronic transformation that subsequently altered the binding properties at neighbouring metal sites. Here we illustrate this concept through the selective adsorption of carbon monoxide (CO) in a series of metal-organic frameworks featuring coordinatively unsaturated iron(ii) sites. Functioning via a mechanism by which neighbouring iron(ii) sites undergo a spin-state transition above a threshold CO pressure, these materials exhibit large CO separation capacities with only small changes in temperature. The very low regeneration energies that result may enable more efficient Fischer-Tropsch conversions and extraction of CO from industrial waste feeds, which currently underutilize this versatile carbon synthon. The electronic basis for the cooperative adsorption demonstrated here could provide a general strategy for designing efficient and selective adsorbents suitable for various separations.

  20. A spin transition mechanism for cooperative adsorption in metal–organic frameworks

    Science.gov (United States)

    Reed, Douglas A.; Keitz, Benjamin K.; Oktawiec, Julia; Mason, Jarad A.; Runčevski, Tomče; Xiao, Dianne J.; Darago, Lucy E.; Crocellà, Valentina; Bordiga, Silvia; Long, Jeffrey R.

    2017-10-01

    Cooperative binding, whereby an initial binding event facilitates the uptake of additional substrate molecules, is common in biological systems such as haemoglobin. It was recently shown that porous solids that exhibit cooperative binding have substantial energetic benefits over traditional adsorbents, but few guidelines currently exist for the design of such materials. In principle, metal–organic frameworks that contain coordinatively unsaturated metal centres could act as both selective and cooperative adsorbents if guest binding at one site were to trigger an electronic transformation that subsequently altered the binding properties at neighbouring metal sites. Here we illustrate this concept through the selective adsorption of carbon monoxide (CO) in a series of metal–organic frameworks featuring coordinatively unsaturated iron(II) sites. Functioning via a mechanism by which neighbouring iron(II) sites undergo a spin-state transition above a threshold CO pressure, these materials exhibit large CO separation capacities with only small changes in temperature. The very low regeneration energies that result may enable more efficient Fischer–Tropsch conversions and extraction of CO from industrial waste feeds, which currently underutilize this versatile carbon synthon. The electronic basis for the cooperative adsorption demonstrated here could provide a general strategy for designing efficient and selective adsorbents suitable for various separations.

  1. Ground state and magnetic phase transitions of the spin Lieb nanolattice: Monte Carlo simulations

    Science.gov (United States)

    Masrour, R.; Jabar, A.

    2018-02-01

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

  2. Topological phase transition of a fractal spin system: The relevance of the network complexity

    Directory of Open Access Journals (Sweden)

    Felipe Torres

    2016-05-01

    Full Text Available A new type of collective excitations, due to the topology of a complex random network that can be characterized by a fractal dimension DF, is investigated. We show analytically that these excitations generate phase transitions due to the non-periodic topology of the DF > 1 complex network. An Ising system, with long range interactions, is studied in detail to support the claim. The analytic treatment is possible because the evaluation of the partition function can be decomposed into closed factor loops, in spite of the architectural complexity. The removal of the infrared divergences leads to an unconventional phase transition, with spin correlations that are robust against thermal fluctuations.

  3. Robust spin crossover platforms with synchronized spin switch and polymer phase transition

    Science.gov (United States)

    Novio, F.; Evangelio, E.; Vazquez-Mera, N.; González-Monje, P.; Bellido, E.; Mendes, S.; Kehagias, N.; Ruiz-Molina, D.

    2013-04-01

    The idea of developing magnetic molecular materials into real functional electronic devices with low-cost and scalable techniques appeared with the emergence of the field several years ago. Today, even though great advances have been done with this aim, the promise of a functional device working at the micro-/nanoscale and at room temperature has unfortunately not completely materialized yet, as their use still strongly depends on the fabrication methodology of a robust device that can be handled and integrated without compromising their functionality. Here we propose the use of polymeric matrices as a platform for the development of such robust switchable structures exhibiting reproducible results independently of the dimension -from macro to micro-/nanoscale- and morphology -from thin-films to nanoparticles and nanoimprinted motives- while allowing to induce an irreversible hysteresis, reminiscent of a non-volatile memory, by synchronization with the polymer phase transition.

  4. Robust spin crossover platforms with synchronized spin switch and polymer phase transition

    Science.gov (United States)

    Novio, F.; Evangelio, E.; Vazquez-Mera, N.; González-Monje, P.; Bellido, E.; Mendes, S.; Kehagias, N.; Ruiz-Molina, D.

    2013-01-01

    The idea of developing magnetic molecular materials into real functional electronic devices with low-cost and scalable techniques appeared with the emergence of the field several years ago. Today, even though great advances have been done with this aim, the promise of a functional device working at the micro-/nanoscale and at room temperature has unfortunately not completely materialized yet, as their use still strongly depends on the fabrication methodology of a robust device that can be handled and integrated without compromising their functionality. Here we propose the use of polymeric matrices as a platform for the development of such robust switchable structures exhibiting reproducible results independently of the dimension -from macro to micro-/nanoscale- and morphology -from thin-films to nanoparticles and nanoimprinted motives- while allowing to induce an irreversible hysteresis, reminiscent of a non-volatile memory, by synchronization with the polymer phase transition.

  5. Continuous Mott transition between a metal and a quantum spin liquid

    Science.gov (United States)

    Mishmash, Ryan V.; González, Iván; Melko, Roger G.; Motrunich, Olexei I.; Fisher, Matthew P. A.

    2015-06-01

    More than half a century after first being proposed by Sir Nevill Mott, the deceptively simple question of whether the interaction-driven electronic metal-insulator transition may be continuous remains enigmatic. Recent experiments on two-dimensional materials suggest that when the insulator is a quantum spin liquid, lack of magnetic long-range order on the insulating side may cause the transition to be continuous, or only very weakly first order. Motivated by this, we study a half-filled extended Hubbard model on a triangular lattice strip geometry. We argue, through use of large-scale numerical simulations and analytical bosonization, that this model harbors a continuous (Kosterlitz-Thouless-like) quantum phase transition between a metal and a gapless spin liquid characterized by a spinon Fermi surface, i.e., a "spinon metal." These results may provide a rare insight into the development of Mott criticality in strongly interacting two-dimensional materials and represent one of the first numerical demonstrations of a Mott insulating quantum spin liquid phase in a genuinely electronic microscopic model.

  6. Field-Induced Spin-State Transition in LaCo1-xMxO3 (M = Al, Ga, Rh, and Ir)

    Science.gov (United States)

    Sato, Keisuke; Matsuo, Akira; Kindo, Koichi; Hara, Yoshiaki; Nakaoka, Kanichiro; Kobayashi, Yoshihiko; Asai, Kichizo

    2014-11-01

    We have investigated the high-field magnetization of lightly doped LaCo1-xMxO3 with M = Al, Ga, Rh, and Ir up to 67 T. The transition field for the field-induced spin-state transition at 4.2 K, which is μ0Hc = 60 T in LaCoO3, increases slightly for M = Al but does not change for M = Ga. On the other hand, the transition field decreases remarkably for M = Rh and Ir. The substitution effect on μ0Hc has been interpreted as arising from the lattice-volume dependence of the excitation energy ΔI of CoI from the low-spin (LS) to high-spin (HS) state. The fraction of CoI is 15% of the total number of Co ions. The remaining Co ions, CoII, are excited from the LS to intermediate-spin (IS) state and contribute to the magnetization at high temperatures above 100 K. We propose the coexistence of the HS and IS states in LaCo1-xMxO3. For M = Rh and Ir, Co species with the magnetic ground state, CoIII, are populated by their substitution. The formation mechanism and spin states of CoIII are discussed in comparison with those of the magnetic Co species in La1-xSrxCoO3.

  7. Dynamics and supramolecular organization of the 1D spin transition polymeric chain compound [Fe(NH2trz)3](NO3)2. Muon spin relaxation.

    Science.gov (United States)

    Garcia, Yann; Campbell, Stewart J; Lord, James S; Boland, Yves; Ksenofontov, Vadim; Gütlich, Philipp

    2007-09-27

    The thermal spin transition that occurs in the polymeric chain compound [Fe(NH(2)trz)3](NO3)2 above room temperature has been investigated by zero-field muon spin relaxation (microSR) over the temperature range approximately 8-402 K. The depolarization curves are best described by a Lorentzian and a Gaussian line that represent fast and slow components, respectively. The spin transition is associated with a hysteresis loop of width DeltaT = 34 K (T1/2 upward arrow = 346 K and T1/2 downward arrow = 312 K) that has been delineated by the temperature variation of the initial asymmetry parameter, in good agreement with previously published magnetic measurements. Zero-field and applied field (20-2000 Oe) microSR measurements show the presence of diamagnetic muon species and paramagnetic muonium radical species (A = 753 +/- 77 MHz) over the entire temperature range. Fast dynamics have been revealed in the high-spin state of [Fe(NH(2)trz)3](NO3)2 with the presence of a Gaussian relaxation mode that is mostly due to the dipolar interaction with static nuclear moments. This situation, where the muonium radicals are totally decoupled and not able to sense paramagnetic fluctuations, implies that the high-spin dynamics fall outside the muon time scale. Insights to the origin of the cooperative effects associated with the spin transition of [Fe(NH(2)trz)3](NO3)2 through muon implantation are presented.

  8. Adaptive Competition, Market Efficiency, Phase Transitions and Spin-Glasses

    CERN Document Server

    Savit, R; Riolo, R; Savit, Robert; Manuca, Radu; Riolo, Rick

    1997-01-01

    We analyze a simple model of adaptive competition which captures essential features of a variety of adaptive competitive systems in the social and biological sciences. Each of N agents, at each time step of a game, joins one of two groups. The agents in the minority group are awarded a point, while the agents in the majority group get nothing. Each agent has a fixed set of strategies drawn at the beginning of the game from a common pool, and chooses his current best-performing strategy to determine which group to join. For a fixed N, the system exhibits a phase change as a function of the size of the common strategy pool from which the agents initially draw their strategies. For small pool sizes, the system is in an efficient market phase. All information that can be used by the agents' strategies is traded away, no agent can accumulate more points than would an agent making random guesses, and thus the commons suffer,since relatively few points are awarded to the agents in total. For large initial strategy p...

  9. Magnetic-field dependence of strongly anisotropic spin reorientation transition in NdFeO3: a terahertz study.

    Science.gov (United States)

    Jiang, Junjie; Song, Gaibei; Wang, Dongyang; Jin, Zuanming; Tian, Zhen; Lin, Xian; Han, Jiaguang; Ma, Guohong; Cao, Shixun; Cheng, Zhenxiang

    2016-03-23

    One of the biggest challenges in spintronics is finding how to switch the magnetization of a material. One way of the spin switching is the spin reorientation transition (SRT), a switching of macroscopic magnetization rotated by 90°. The macroscopic magnetization in a NdFeO3 single crystal rotates from Γ4 to Γ2 via Γ24 as the temperature is decreased from 170 to 100 K, while it can be switched back to Γ4 again by increasing the temperature. However, the precise roles of the magnetic-field induced SRT are still unclear. By using terahertz time-domain spectroscopy (THz-TDS), here, we show that the magnetic-field induced SRT between Γ4 and Γ2 is strongly anisotropic, depending on the direction of the applied magnetic field. Our experimental results are well interpreted by the anisotropy of rare-earth Nd(3+) ion. Furthermore, we find that the critical magnetic-field required for SRT can be modified by changing the temperature. Our study suggests that the anisotropic SRT in NdFeO3 single crystal provides a platform to facilitate the potential applications in robust spin memory devices.

  10. Manipulation of the large Rashba spin splitting in polar two-dimensional transition-metal dichalcogenides

    Science.gov (United States)

    Yao, Qun-Fang; Cai, Jia; Tong, Wen-Yi; Gong, Shi-Jing; Wang, Ji-Qing; Wan, Xiangang; Duan, Chun-Gang; Chu, J. H.

    2017-04-01

    Transition-metal dichalcogenide (TMD) monolayers M X Y (M =Mo ,W ;X ≠Y =S ,Se ,Te ) are two-dimensional polar semiconductors. Setting the WSeTe monolayer as an example and using density functional theory calculations, we investigate the manipulation of Rashba spin-orbit coupling (SOC) in the MXY monolayer. It is found that the intrinsic out-of-plane electric field due to the mirror symmetry breaking induces the large Rashba spin splitting around the Γ point, which, however, can be easily tuned by applying the in-plane biaxial strain. Through a relatively small strain (from -2 % to 2%), a large tunability (from around -50 % to 50%) of Rashba SOC can be obtained due to the modified orbital overlap, which can in turn modulate the intrinsic electric field. The orbital selective external potential method further confirms the significance of the orbital overlap between W -dz2 and Se -pz in Rashba SOC. In addition, we also explore the influence of the external electric field on Rashba SOC in the WSeTe monolayer, which is less effective than strain. By calculating the electric-field-induced Rashba SOC in all six M X2 monolayers, the rule of the electric-field influence on Rashba SOC in TMD monolayers is demonstrated. The large Rashba spin splitting, together with the valley spin splitting in MXY monolayers, may make a special contribution to semiconductor spintronics and valleytronics.

  11. Engineering electrocatalytic activity in nanosized perovskite cobaltite through surface spin-state transition

    Science.gov (United States)

    Zhou, Shiming; Miao, Xianbing; Zhao, Xu; Ma, Chao; Qiu, Yuhao; Hu, Zhenpeng; Zhao, Jiyin; Shi, Lei; Zeng, Jie

    2016-05-01

    The activity of electrocatalysts exhibits a strongly dependence on their electronic structures. Specifically, for perovskite oxides, Shao-Horn and co-workers have reported a correlation between the oxygen evolution reaction activity and the eg orbital occupation of transition-metal ions, which provides guidelines for the design of highly active catalysts. Here we demonstrate a facile method to engineer the eg filling of perovskite cobaltite LaCoO3 for improving the oxygen evolution reaction activity. By reducing the particle size to ~80 nm, the eg filling of cobalt ions is successfully increased from unity to near the optimal configuration of 1.2 expected by Shao-Horn's principle. Consequently, the activity is significantly enhanced, comparable to those of recently reported cobalt oxides with eg~1.2 configurations. This enhancement is ascribed to the emergence of spin-state transition from low-spin to high-spin states for cobalt ions at the surface of the nanoparticles, leading to more active sites with increased reactivity.

  12. Phase transition in SbCl 5 - graphite studied by spin resonance experiments

    Science.gov (United States)

    Rolla, S.; Walmsley, L.; Suematsu, H.; Torriani, I.; Rettori, C.; Yosida, Y.

    1986-05-01

    Conduction Carrier Spin Resonance (CCSR) experiments in stage 3 and 4 acceptor SbCl 5 - Graphite Intercalated Compounds (GICs) reveal an almost stage independent phase transition at T c ≋ 225K. The CCSR linewidth shows an anomalous broadening below T c, which is observable only when the sample is kept in a region close to T c (190-225K); the broadening was not observed for rapid cooling. This broadening has a much faster kinetics for heating than for cooling rum. These thermal hysteresis and kinetics are quite similar to those found in AlCl 3-GICs. We attribute this phase transition to the quasi-2D "solid liquid" transformation experienced by the minority molecules of SbCl 3 present among the intercalated species in SbCl 5-GICs, proposed by Homma and Clarke. For stage 2 data does not show evidences of this phase transition.

  13. Investigating Quantum Phase Transitions in Spin-2 AKLT Systems with Tensor Networks

    Science.gov (United States)

    Pomata, Nicholas; Huang, Ching-Yu; Wei, Tzu-Chieh

    The spin-2 Affleck-Kennedy-Lieb-Tasaki (AKLT) state on the square lattice, a valence-bond solid (VBS) state, has nontrivial symmetry-protected topological order when translation and rotation invariance are imposed. Niggemann, Klümper, and Zittartz previously studied a two-parameter deformation of this state from the AKLT point, which exhibits a second-order phase transition from a disordered VBS phase to a Neel-ordered phase. We re-examine the deformed AKLT model using tensor renormalization methods. In addition to recovering the VBS-Neel transition, we find new transitions into XY-like and product-state phases, which we can characterize using local order parameters and modular matrices.

  14. Modeling nonequilibrium dynamics of phase transitions at the nanoscale: Application to spin-crossover.

    Science.gov (United States)

    Park, Sang Tae; van der Veen, Renske M

    2017-07-01

    In this article, we present a continuum mechanics based approach for modeling thermally induced single-nanoparticle phase transitions studied in ultrafast electron microscopy. By using coupled differential equations describing heat transfer and the kinetics of the phase transition, we determine the major factors governing the time scales and efficiencies of thermal switching in individual spin-crossover nanoparticles, such as the thermal properties of the (graphite) substrate, the particle thickness, and the interfacial thermal contact conductance between the substrate and the nanoparticle. By comparing the simulated dynamics with the experimental single-particle diffraction time profiles, we demonstrate that the proposed non-equilibrium phase transition model can fully account for the observed switching dynamics.

  15. Modeling nonequilibrium dynamics of phase transitions at the nanoscale: Application to spin-crossover

    Directory of Open Access Journals (Sweden)

    Sang Tae Park

    2017-07-01

    Full Text Available In this article, we present a continuum mechanics based approach for modeling thermally induced single-nanoparticle phase transitions studied in ultrafast electron microscopy. By using coupled differential equations describing heat transfer and the kinetics of the phase transition, we determine the major factors governing the time scales and efficiencies of thermal switching in individual spin-crossover nanoparticles, such as the thermal properties of the (graphite substrate, the particle thickness, and the interfacial thermal contact conductance between the substrate and the nanoparticle. By comparing the simulated dynamics with the experimental single-particle diffraction time profiles, we demonstrate that the proposed non-equilibrium phase transition model can fully account for the observed switching dynamics.

  16. Technical change during the energy transition

    NARCIS (Netherlands)

    van der Meijden, G.C.; Smulders, Sjak

    The energy transition from fossil fuels to alternative energy sources has important consequences for technological change and resource extraction. We examine these consequences by incorporating a non-renewable resource and an alternative energy source in a market economy model of endogenous growth

  17. Technological Change During the Energy Transition

    NARCIS (Netherlands)

    van der Meijden, G.C.; Smulders, Sjak A.

    2014-01-01

    The energy transition from fossil fuels to alternative energy sources has important consequences for technological change and resource extraction. We examine these consequences by incorporating a non-renewable resource and an alternative energy source in a market economy model of endogenous growth

  18. Technological Change during the Energy Transition

    NARCIS (Netherlands)

    van der Meijden, G.C.; Smulders, J.A.

    2014-01-01

    The energy transition from fossil fuels to alternative energy sources has important consequences for technological change and resource extraction. We examine these consequences by incorporating a non-renewable resource and an alternative energy source in a market economy model of endogenous growth

  19. Control over the magnetism and transition between high- and low-spin states of an adatom on trilayer graphene.

    Science.gov (United States)

    Zheng, Anmin; Gao, Guoying; Huang, Hai; Gao, Jinhua; Yao, Kailun

    2017-05-31

    Using density-functional theory, we investigate the electronic and magnetic properties of an adatom (Na, Cu and Fe) on ABA- and ABC-stacked (Bernal and rhombohedral) trilayer graphenes. In particular, we study the influence of an applied gate voltage on magnetism, as it modifies the electronic states of the trilayer graphene (TLG) as well as changes the adatom spin states. Our study performed for a choice of three different adatoms (Na, Cu, and Fe) shows that the nature of adatom-graphene bonding evolves from ionic to covalent in moving from an alkali metal (Na) to a transition metal (Cu or Fe). Applying an external electric field (EEF) to TLG systems with different stacking orders results in the transition between high- and low-spin states in the latter case (Cu, Fe) and induces a little of magnetism in the former (Na) without magnetism in the absence of an external electric field. Our study would be useful for controlled adatom magnetism and (organic) spintronic applications in nanotechnology.

  20. Spin-state transition in LaCoO3: direct neutron spectroscopic evidence of excited magnetic states.

    Science.gov (United States)

    Podlesnyak, A; Streule, S; Mesot, J; Medarde, M; Pomjakushina, E; Conder, K; Tanaka, A; Haverkort, M W; Khomskii, D I

    2006-12-15

    A gradual spin-state transition occurs in LaCoO3 around T approximately 80-120 K, whose detailed nature remains controversial. We studied this transition by means of inelastic neutron scattering and found that with increasing temperature an excitation at approximately 0.6 meV appears, whose intensity increases with temperature, following the bulk magnetization. Within a model including crystal-field interaction and spin-orbit coupling, we interpret this excitation as originating from a transition between thermally excited states located about 120 K above the ground state. We further discuss the nature of the magnetic excited state in terms of intermediate-spin (t(2g)(5)e(g)(1), S=1) versus high-spin (t(2g)(4)e(g)(2), S=2) states. Since the g factor obtained from the field dependence of the inelastic neutron scattering is g approximately 3, the second interpretation is definitely favored.

  1. Localization-delocalization transition in spin-orbit-coupled Bose-Einstein condensate

    Science.gov (United States)

    Li, Chunyan; Ye, Fangwei; Kartashov, Yaroslav V.; Konotop, Vladimir V.; Chen, Xianfeng

    2016-08-01

    We address the impact of the spin-orbit (SO) coupling on the localization-delocalization-transition (LDT) in a spin-orbit coupled Bose-Einstein condensate in a bichromatic potential. We find that SO coupling significantly alters the threshold depth of the one of sublattices above which the lowest eigenstates transform from delocalizated into localized. For some moderate coupling strengths the threshold is strongly reduced, which is explained by the SO coupling-induced band flattening in one of the sub-lattices. We explain why simultaneous Rabi and SO coupling are necessary ingredients for LDT threshold cancellation and show that strong SO coupling drives the system into the state where its evolution becomes similar to the evolution of a one-component system. We also find that defocusing nonlinearity can lead to localization of the states which are delocalized in the linear limit.

  2. Localization-delocalization transition in spin-orbit-coupled Bose-Einstein condensate

    Science.gov (United States)

    Li, Chunyan; Ye, Fangwei; Kartashov, Yaroslav V.; Konotop, Vladimir V.; Chen, Xianfeng

    2016-01-01

    We address the impact of the spin-orbit (SO) coupling on the localization-delocalization-transition (LDT) in a spin-orbit coupled Bose-Einstein condensate in a bichromatic potential. We find that SO coupling significantly alters the threshold depth of the one of sublattices above which the lowest eigenstates transform from delocalizated into localized. For some moderate coupling strengths the threshold is strongly reduced, which is explained by the SO coupling-induced band flattening in one of the sub-lattices. We explain why simultaneous Rabi and SO coupling are necessary ingredients for LDT threshold cancellation and show that strong SO coupling drives the system into the state where its evolution becomes similar to the evolution of a one-component system. We also find that defocusing nonlinearity can lead to localization of the states which are delocalized in the linear limit. PMID:27531120

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

    Science.gov (United States)

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

    2008-12-01

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

  4. Unravelling the chemical design of spin-crossover nanoparticles based on iron(ii)-triazole coordination polymers: towards a control of the spin transition.

    Science.gov (United States)

    Giménez-Marqués, Mónica; García-Sanz de Larrea, M Luisa; Coronado, Eugenio

    2015-08-14

    A systematic study of the key synthetic parameters that control the growth of spin-crossover (SCO) nanoparticles (NPs) using the reverse micelle technique has been undertaken in the system [Fe(Htrz)2(trz)](BF4)·H2O, (Htrz = 1,2,4-triazole). This has permitted us to modulate the physical properties of the NPs in a controlled and reproducible manner. In particular, a control over the size of the NPs (in the range 4 to 16 nm) has been achieved by varying the water to surfactant molar ratio. The consequences of this size variation on the cooperativity of the spin transition are discussed. Finally, this approach has been extended to the chemical alloy [Fe(Htrz)2.95(NH2trz)0.05](ClO4)2 in order to prepare NPs exhibiting a cooperative and hysteretic spin transition centred closer to room temperature.

  5. Detection of individual spin transitions of a single proton confined in a cryogenic Penning trap

    Energy Technology Data Exchange (ETDEWEB)

    Kracke, Holger

    2013-02-27

    The presented experiment for the determination of the magnetic moment of the proton is based on the measurement of the ratio of cyclotron frequency and Larmor frequency of a single proton confined in a cryogenic double-Penning trap. In the course of this thesis, the simultaneous non-destructive measurement of two of the three eigenfrequencies of the proton in thermal equilibrium with corresponding detection systems was demonstrated, which reduces the measurement time of the cyclotron frequency by a factor of two. Furthermore, this thesis presents the first detection of individual spin transitions of a single proton, which allows for the determination of the Larmor frequency. The continuous Stern-Gerlach effect is utilized to couple the magnetic moment to the axial mode of the trapped proton by means of a magnetic bottle. Thus, a spin flip causes a jump of the axial frequency, which can be measured non-destructively with highly-sensitive detection systems. However, not only the spin momentum is coupled to the axial motion but also the angular momentum. Thus, the main experimental challenge is the elimination of energy fluctuations in the radial modes in order to maintain spin flip resolution. Due to systematic studies on the stability of the axial frequency and a complete revision of the experimental setup, this goal was achieved. The spin state of the proton can be determined with very high fidelity for the very first time. Thus, this thesis represents an important step towards a high-precision determination of the magnetic moment of the proton.

  6. Viscosity undulations in the lower mantle: The dynamical role of iron spin transition

    Science.gov (United States)

    Justo, J. F.; Morra, G.; Yuen, D. A.

    2015-07-01

    A proper determination of the lower-mantle viscosity profile is fundamental to understanding Earth geodynamics. Based on results coming from different sources, several models have been proposed to constrain the variations of viscosity as a function of pressure, stress and temperature. While some models have proposed a relatively modest viscosity variation across the lower mantle, others have proposed variations of several orders of magnitude. Here, we have determined the viscosity of ferropericlase, a major mantle mineral, and explored the role of the iron high-to-low spin transition. Viscosity was described within the elastic strain energy model, in which the activation parameters are obtained from the bulk and shear wave velocities. Those velocities were computed combining first principles total energy calculations and the quasi-harmonic approximation. As a result of a strong elasticity softening across the spin transition, there is a large reduction in the activation free energies of the materials creep properties, leading to viscosity undulations. These results suggest that the variations of the viscosity across the lower mantle, resulting from geoid inversion and postglacial rebound studies, may be caused by the iron spin transition in mantle minerals. Implications of the undulated lower mantle viscosity profile exist for both, down- and up-wellings in the mantle. We find that a viscosity profile characterized by an activation free energy of G* (z0) ˜ 300- 400 kJ /mol based on diffusion creep and dilation factor δ = 0.5 better fits the observed high velocity layer at mid mantle depths, which can be explained by the stagnation and mixing of mantle material. Our model also accounts for the growth of mantle plume heads up to the size necessary to explain the Large Igneous Provinces that characterize the start of most plume tracks.

  7. Responses to Change Helping People Make Transitions

    CERN Document Server

    (CCL), Center for Creative Leadership

    2011-01-01

    The ongoing state of many organizations is one of change. People who experience major change tend to exhibit one of four patterns of response: entrenched, overwhelmed, poser, or learner. As a leader, you need to understand the patterns of response that people express and to customize intervention strategies to help them make the transition. People can pass through a given response stage and move to one that is more effective--especially if you provide timely intervention and support. This guidebook will help you understand how people, including yourself, are responding to change and what you c

  8. Magnetoelectric effect near spin reorientation transition in giant magnetostrictive-aluminum nitride thin film structure

    Science.gov (United States)

    Tiercelin, Nicolas; Talbi, A.; Preobrazhensky, V.; Pernod, P.; Mortet, V.; Haenen, K.; Soltani, A.

    2008-10-01

    Hybrid giant magnetostrictive-piezoelectric film/film structures exhibiting magnetoelectric (ME) effect associated with a magnetic instability of the spin reorientation transition type are presented. We first present the theoretical study of a clamped beam actuator composed of a piezoelectric layer on a substrate actuated by a magnetostrictive layer. The actuator is a polished 50 μm thick 18×5 mm2 silicon substrate coated by an electrode, aluminum nitride, and magnetostrictive nanostructured layer. A ME coefficient of 30 V Oe-1 cm-1 at a 35 KHz longitudinal resonance was measured. Nonlinear excitation of this mode showed a "nonlinear" dynamic ME coefficient of 4 V Oe-1 cm-1.

  9. Vison states and confinement transitions of Z2 spin liquids on the kagome lattice

    Science.gov (United States)

    Huh, Yejin; Punk, Matthias; Sachdev, Subir

    2011-09-01

    We present a projective symmetry group (PSG) analysis of the spinless excitations of Z2 spin liquids on the kagome lattice. In the simplest case, vortices carrying Z2 magnetic flux (“visons”) are shown to transform under the 48 element group GL(2,Z3). Alternative exchange couplings can also lead to a second case with visons transforming under 288-element group GL(2,Z3)×D3. We study the quantum phase transition in which visons condense into confining states with valence bond solid order. The critical field theories and confining states are classified using the vison PSGs.

  10. Effects of the Fe 3 + spin transition on the properties of aluminous perovskite—New insights for lower-mantle seismic heterogeneities

    Science.gov (United States)

    Catalli, Krystle; Shim, Sang-Heon; Dera, Przemyslaw; Prakapenka, Vitali B.; Zhao, Jiyong; Sturhahn, Wolfgang; Chow, Paul; Xiao, Yuming; Cynn, Hyunchae; Evans, William J.

    2011-10-01

    We have measured the effects of the coupled substitution of Fe 3 + and Al on the density and compressibility of mantle silicate perovskite (Pv) up to 95 GPa. X-ray emission spectroscopy and synchrotron Mössbauer spectroscopy reveal a rapid increase in the population of low-spin Fe 3 + in Fe 3 + , Al-bearing Pv over a narrow pressure range near 70 GPa, which is in sharp contrast with Al-free Fe 3 + -bearing Pv, where Fe 3 + undergoes a gradual spin transition, and with Al-free Fe 2 + -bearing Pv, where Fe 2 + does not become low spin. At low pressure, Fe 3 + and Al expand the perovskite lattice. However, near the pressure range of the abrupt increase in the low-spin population, the unit-cell volume of Fe 3 + , Al-bearing Pv becomes similar to that of Mg-endmember Pv, while those of Al-free Fe 3 + -bearing Pv and Al-free Fe 2 + -bearing Pv remain larger throughout the lower mantle. Consequently, Pv in Al-rich systems should have lower density in the shallow lower mantle but similar or greater density than Pv in pyrolite in the deep lower mantle, affecting the buoyancy and mechanical stability of heterogeneities. Although the Fe 3 + spin transition in Pv is unlikely to cause a seismic discontinuity at mantle temperatures, it may result in a large change in bulk sound speed at 1200-1800 km depth, such that a vertically extending structure with an elevated amount of Fe 3 + would generate slower and faster anomalies above and below the depth of the spin transition, respectively, relative to the surrounding mantle. This may have important implications for bulk sound speed anomalies observed at similar depths in seismic tomography studies.

  11. Pressure induced iron spin state changes in MgGeO3 Perovskite and Post-perovskite

    Science.gov (United States)

    Sarkar, Kanchan; Shukla, Gaurav; Topsakal, Mehmet; Wentzcovitch, Renata

    2015-03-01

    MgGeO3-perovskite is a low pressure analog of MgSiO3-perovskite, the main Earth forming phase, and is used to shed light on several phenomena that occur in MgSiO3, particularly the post-perovskite transition. As such, experimental investigations of spin state changes in Fe-bearing MgGeO3 might help to clarify some aspects of this phenomenon in MgSiO3. Using DFT+U calculations, we have investigated pressure induced spin state changes in Fe2+ and Fe3+ in MgGeO3 perovskite and post-perovskite and their effect on the post-perovskite transition. We uncover a direct relationship between average Fe-O bond-lengths and spin transition pressures in all cases. The effect of iron on the post-perovskite transitions in these phases can also be related to the average Fe-O bond lengths. Research supported by NSF/EAR and NSF/CAREER.

  12. Size-change termination and transition invariants

    DEFF Research Database (Denmark)

    Heizmann, Matthias; Jones, Neil; Podelski, Andreas

    2010-01-01

    Two directions of recent work on program termination use the concepts of size-change termination resp. transition invariants. The difference in the setting has as consequence the inherent incomparability of the analysis and verification methods that result from this work. Yet, in order to facilit...... to facilitate the crossover of ideas and techniques in further developments, it seems interesting to identify which aspects in the respective formal foundation are related. This paper presents initial results in this direction....

  13. Relaxation theory of spin-3/2 Ising system near phase transition temperatures

    Science.gov (United States)

    Osman, Canko; Mustafa, Keskin

    2010-08-01

    Dynamics of a spin-3/2 Ising system Hamiltonian with bilinear and biquadratic nearest-neighbour exchange interactions is studied by a simple method in which the statistical equilibrium theory is combined with the Onsager's theory of irreversible thermodynamics. First, the equilibrium behaviour of the model in the molecular-field approximation is given briefly in order to obtain the phase transition temperatures, i.e. the first- and second-order and the tricritical points. Then, the Onsager theory is applied to the model and the kinetic or rate equations are obtained. By solving these equations three relaxation times are calculated and their behaviours are examined for temperatures near the phase transition points. Moreover, the z dynamic critical exponent is calculated and compared with the z values obtained for different systems experimentally and theoretically, and they are found to be in good agrement.

  14. Quantum coherence of an XY spin chain with Dzyaloshinskii-Moriya interaction and quantum phase transition

    Science.gov (United States)

    Zhang, Guo-Qing; Xu, Jing-Bo

    2017-06-01

    We investigate the quantum coherence of an XY spin chain with Dzyaloshinskii-Moriya interaction using a quantum renormalization group-based method, and show that the relative entropy of coherence increases with Dzyaloshinskii-Moriya interaction strength at zero temperature, as well as at finite temperature. We also study the quantum criticality of the system by making use of the relative entropy of coherence and violation of Bell inequality, and find that the first derivatives of the renormalized quantum coherence exhibit singularity near the critical point of the quantum phase transition. Finally, we explore the finite-size scaling behaviors of the derivatives of the quantum coherence at the critical point of the quantum phase transition, and obtain several universal finite-size scaling laws.

  15. Metal-insulator transition in SrIrO3 with strong spin-orbit interaction.

    Science.gov (United States)

    Wu, Fei-Xiang; Zhou, Jian; Zhang, L Y; Chen, Y B; Zhang, Shan-Tao; Gu, Zheng-Bin; Yao, Shu-Hua; Chen, Yan-Feng

    2013-03-27

    The thickness-dependent metal-insulator transition is observed in meta-stable orthorhombic SrIrO3 thin films synthesized by pulsed laser deposition. SrIrO3 films with thicknesses less than 3 nm demonstrate insulating behaviour, whereas those thicker than 4 nm exhibit metallic conductivity at high temperature, and insulating-like behaviour at low temperature. Weak/Anderson localization is mainly responsible for the observed thickness-dependent metal-insulator transition in SrIrO3 films. Temperature-dependent resistance fitting shows that electrical-conductivity carriers are mainly scattered by the electron-boson interaction rather than the electron-electron interaction. Analysis of the magneto-conductance proves that the spin-orbit interaction plays a crucial role in the magneto-conductance property of SrIrO3.

  16. The effect of temperature and external field on transitions in elements of kagome spin ice

    Science.gov (United States)

    Liashko, Sergei Y.; Jónsson, Hannes; Uzdin, Valery M.

    2017-11-01

    Transitions between magnetic states of one and two ring kagome spin ice elements consisting of 6 and 11 prolate magnetic islands are calculated and the lifetime of the ground states evaluated using harmonic transition state theory and the stationary state approximation. The calculated values are in close agreement with experimental lifetime measurements made by Farhan and co-workers (Farhan et al 2013 Nat. Phys. 9 375) when values of the parameters in the Hamiltonian are chosen to be best estimates for a single island, obtained from measurements and micromagnetic modeling. The effective pre-exponential factor in the Arrhenius rate law for the elementary steps turns out to be quite small, on the order of 109 s‑1, three orders of magnitude smaller than has been assumed in previous analysis of the experimental data, while the effective activation energy is correspondingly lower than the previous estimate. The application of an external magnetic field is found to strongly affect the energy landscape of the system. Even a field of 4 {{mT}} can eliminate states that correspond to ground states in the absence of a field. The theoretical approach presented here and the close agreement found with experimental data demonstrates that the properties of spin ice systems can be calculated using the tools of rate theory and a Hamiltonian parametrized only from the properties of a single island.

  17. Exact phase boundaries and topological phase transitions of the X Y Z spin chain

    Science.gov (United States)

    Jafari, S. A.

    2017-07-01

    Within the block spin renormalization group, we give a very simple derivation of the exact phase boundaries of the X Y Z spin chain. First, we identify the Ising order along x ̂ or y ̂ as attractive renormalization group fixed points of the Kitaev chain. Then, in a global phase space composed of the anisotropy λ of the X Y interaction and the coupling Δ of the Δ σzσz interaction, we find that the above fixed points remain attractive in the two-dimesional parameter space. We therefore classify the gapped phases of the X Y Z spin chain as: (1) either attracted to the Ising limit of the Kitaev-chain, which in turn is characterized by winding number ±1 , depending on whether the Ising order parameter is along x ̂ or y ̂ directions; or (2) attracted to the charge density wave (CDW) phases of the underlying Jordan-Wigner fermions, which is characterized by zero winding number. We therefore establish that the exact phase boundaries of the X Y Z model in Baxter's solution indeed correspond to topological phase transitions. The topological nature of the phase transitions of the X Y Z model justifies why our analytical solution of the three-site problem that is at the core of the present renormalization group treatment is able to produce the exact phase boundaries of Baxter's solution. We argue that the distribution of the winding numbers between the three Ising phases is a matter of choice of the coordinate system, and therefore the CDW-Ising phase is entitled to host appropriate form of zero modes. We further observe that in the Kitaev-chain the renormalization group flow can be cast into a geometric progression of a properly identified parameter. We show that this new parameter is actually the size of the (Majorana) zero modes.

  18. Climate change mitigation through livestock system transitions.

    Science.gov (United States)

    Havlík, Petr; Valin, Hugo; Herrero, Mario; Obersteiner, Michael; Schmid, Erwin; Rufino, Mariana C; Mosnier, Aline; Thornton, Philip K; Böttcher, Hannes; Conant, Richard T; Frank, Stefan; Fritz, Steffen; Fuss, Sabine; Kraxner, Florian; Notenbaert, An

    2014-03-11

    Livestock are responsible for 12% of anthropogenic greenhouse gas emissions. Sustainable intensification of livestock production systems might become a key climate mitigation technology. However, livestock production systems vary substantially, making the implementation of climate mitigation policies a formidable challenge. Here, we provide results from an economic model using a detailed and high-resolution representation of livestock production systems. We project that by 2030 autonomous transitions toward more efficient systems would decrease emissions by 736 million metric tons of carbon dioxide equivalent per year (MtCO2e⋅y(-1)), mainly through avoided emissions from the conversion of 162 Mha of natural land. A moderate mitigation policy targeting emissions from both the agricultural and land-use change sectors with a carbon price of US$10 per tCO2e could lead to an abatement of 3,223 MtCO2e⋅y(-1). Livestock system transitions would contribute 21% of the total abatement, intra- and interregional relocation of livestock production another 40%, and all other mechanisms would add 39%. A comparable abatement of 3,068 MtCO2e⋅y(-1) could be achieved also with a policy targeting only emissions from land-use change. Stringent climate policies might lead to reductions in food availability of up to 200 kcal per capita per day globally. We find that mitigation policies targeting emissions from land-use change are 5 to 10 times more efficient--measured in "total abatement calorie cost"--than policies targeting emissions from livestock only. Thus, fostering transitions toward more productive livestock production systems in combination with climate policies targeting the land-use change appears to be the most efficient lever to deliver desirable climate and food availability outcomes.

  19. Evolution of the phonon density of states of LaCoO3 over the spin state transition

    Energy Technology Data Exchange (ETDEWEB)

    Golosova, N. O. [Joint Institute for Nuclear Research, Dubna, Russia; Kozlenko, D. P. [Joint Institute for Nuclear Research, Dubna, Russia; Kolesnikov, Alexander I [ORNL; Kazimirov, V. Yu. [Joint Institute for Nuclear Research, Dubna, Russia; Smirnov, M. B. [St. Petersburg State University, St. Petersburg, Russia; Jirak, Z. [Institute of Physics, Czech Republic; Savenko, B. N. [Joint Institute for Nuclear Research, Dubna, Russia

    2011-01-01

    The phonon spectra of LaCoO3 were studied by inelastic neutron scattering in the temperature range of 4 120 K. The DFT calculations of the lattice dynamics have been made for interpretation of the experimental data. The observed and calculated phonon frequencies were found to be in a reasonable agreement. The evolution of the phonon density of states over the spin state transition was analyzed. In the low-temperature range (T < 50 K), an increase in the energy of resolved breathing, stretching, and bending phonon modes was found, followed by their softening and broadening at higher temperatures due to the spin state transition and relevant orbital-phonon coupling.

  20. Two-dimensional ferromagnet/semiconductor transition metal dichalcogenide contacts: p-type Schottky barrier and spin-injection control

    KAUST Repository

    Gan, Liyong

    2013-09-26

    We study the ferromagnet/semiconductor contacts formed by transition metal dichalcogenide monolayers, focusing on semiconducting MoS2 and WS2 and ferromagnetic VS2. We investigate the degree of p-type doping and demonstrate tuning of the Schottky barrier height by vertical compressive pressure. An analytical model is presented for the barrier heights that accurately describes the numerical findings and is expected to be of general validity for all transition metal dichalcogenide metal/semiconductor contacts. Furthermore, magnetic proximity effects induce a 100% spin polarization at the Fermi level in the semiconductor where the spin splitting increases up to 0.70 eV for increasing pressure.

  1. Pressure Sensor via Optical Detection Based on a 1D Spin Transition Coordination Polymer

    Directory of Open Access Journals (Sweden)

    Cătălin M. Jureschi

    2015-01-01

    Full Text Available We have investigated the suitability of using the 1D spin crossover coordination polymer [Fe(4-(2’-hydroxyethyl-1,2,4-triazole3]I2∙H2O, known to crossover around room temperature, as a pressure sensor via optical detection using various contact pressures up to 250 MPa. A dramatic persistent colour change is observed. The experimental data, obtained by calorimetric and Mössbauer measurements, have been used for a theoretical analysis, in the framework of the Ising-like model, of the thermal and pressure induced spin state switching. The pressure (P-temperature (T phase diagram calculated for this compound has been used to obtain the P-T bistability region.

  2. Unifying Exchange Sensitivity in Transition-Metal Spin-State Ordering and Catalysis through Bond Valence Metrics.

    Science.gov (United States)

    Gani, Terry Z H; Kulik, Heather J

    2017-11-14

    Accurate predictions of spin-state ordering, reaction energetics, and barrier heights are critical for the computational discovery of open-shell transition-metal (TM) catalysts. Semilocal approximations in density functional theory, such as the generalized gradient approximation (GGA), suffer from delocalization error that causes them to overstabilize strongly bonded states. Descriptions of energetics and bonding are often improved by introducing a fraction of exact exchange (e.g., erroneous low-spin GGA ground states are instead correctly predicted as high-spin with a hybrid functional). The degree of spin-splitting sensitivity to exchange can be understood based on the chemical composition of the complex, but the effect of exchange on reaction energetics within a single spin state is less well-established. Across a number of model iron complexes, we observe strong exchange sensitivities of reaction barriers and energies that are of the same magnitude as those for spin splitting energies. We rationalize trends in both reaction and spin energetics by introducing a measure of delocalization, the bond valence of the metal-ligand bonds in each complex. The bond valence thus represents a simple-to-compute property that unifies understanding of exchange sensitivity for catalytic properties and spin-state ordering in TM complexes. Close agreement of the resulting per-metal-organic-bond sensitivity estimates, together with failure of alternative descriptors demonstrates the utility of the bond valence as a robust descriptor of how differences in metal-ligand delocalization produce differing relative energetics with exchange tuning. Our unified description explains the overall effect of exact exchange tuning on the paradigmatic two-state FeO + /CH 4 reaction that combines challenges of spin-state and reactivity predictions. This new descriptor-sensitivity relationship provides a path to quantifying how predictions in transition-metal complex screening are sensitive to the

  3. Spin Transition in the Lower Mantle: Deep Learning and Pattern Recognition of Superplumes from the Mid-mantle and Mid-mantle Slab Stagnation

    Science.gov (United States)

    Yuen, D. A.; Shahnas, M. H.; De Hoop, M. V.; Pysklywec, R.

    2016-12-01

    The broad, slow seismic anomalies under Africa and Pacific cannot be explained without ambiguity. There is no well-established theory to explain the fast structures prevalent globally in seismic tomographic images that are commonly accepted to be the remnants of fossil slabs at different depths in the mantle. The spin transition from high spin to low spin in iron in ferropericlase and perovskite, two major constituents of the lower mantle can significantly impact their physical properties. We employ high resolution 2D-axisymmetric and 3D-spherical control volume models to reconcile the influence of the spin transition-induced anomalies in density, thermal expansivity, and bulk modulus in ferropericlase and perovskite on mantle dynamics. The model results reveal that the spin transition effects increase the mixing in the lower regions of mantle. Depending on the changes of bulk modulus associated with the spin transition, these effects may also cause both stagnation of slabs and rising plumes at mid-mantle depths ( 1600 km). The stagnation may be followed by downward or upward penetration of cold or hot mantle material, respectively, through an avalanche process. The size of these mid-mantle plumes reaches 1500 km across with a radial velocity reaching 20 cm/yr near the seismic transition zone and plume heads exceeding 2500 km across. We will employ a deep-learning algorithm to formulate this challenge as a classification problem where modelling/computation aids in the learning stage for detecting the particular patterns.The parameters based on which the convection models are developed are poorly constrained. There are uncertainties in initial conditions, heterogeneities and boundary conditions in the simulations, which are nonlinear. Thus it is difficult to reconstruct the past configuration over long time scales. In order to extract information and better understand the parameters in mantle convection, we employ deep learning algorithm to search for different

  4. Quantum Monte Carlo studies of a metallic spin-density wave transition

    Energy Technology Data Exchange (ETDEWEB)

    Gerlach, Max Henner

    2017-01-20

    Plenty experimental evidence indicates that quantum critical phenomena give rise to much of the rich physics observed in strongly correlated itinerant electron systems such as the high temperature superconductors. A quantum critical point of particular interest is found at the zero-temperature onset of spin-density wave order in two-dimensional metals. The appropriate low-energy theory poses an exceptionally hard problem to analytic theory, therefore the unbiased and controlled numerical approach pursued in this thesis provides important contributions on the road to comprehensive understanding. After discussing the phenomenology of quantum criticality, a sign-problem-free determinantal quantum Monte Carlo approach is introduced and an extensive toolbox of numerical methods is described in a self-contained way. By the means of large-scale computer simulations we have solved a lattice realization of the universal effective theory of interest. The finite-temperature phase diagram, showing both a quasi-long-range spin-density wave ordered phase and a d-wave superconducting dome, is discussed in its entirety. Close to the quantum phase transition we find evidence for unusual scaling of the order parameter correlations and for non-Fermi liquid behavior at isolated hot spots on the Fermi surface.

  5. Electronic and magnetic properties of spiral spin-density-wave states in transition-metal chains

    Science.gov (United States)

    Tanveer, M.; Ruiz-Díaz, P.; Pastor, G. M.

    2016-09-01

    The electronic and magnetic properties of one-dimensional (1D) 3 d transition-metal nanowires are investigated in the framework of density functional theory. The relative stability of collinear and noncollinear (NC) ground-state magnetic orders in V, Mn, and Fe monoatomic chains is quantified by computing the frozen-magnon dispersion relation Δ E (q ⃗) as a function of the spin-density-wave vector q ⃗. The dependence on the local environment of the atoms is analyzed by varying systematically the lattice parameter a of the chains. Electron correlation effects are explored by comparing local spin-density and generalized-gradient approximations to the exchange and correlation functional. Results are given for Δ E (q ⃗) , the local magnetic moments μ⃗i at atom i , the magnetization-vector density m ⃗(r ⃗) , and the local electronic density of states ρi σ(ɛ ) . The frozen-magnon dispersion relations are analyzed from a local perspective. Effective exchange interactions Ji j between the local magnetic moments μ⃗i and μ⃗j are derived by fitting the ab initio Δ E (q ⃗) to a classical 1D Heisenberg model. The dominant competing interactions Ji j at the origin of the NC magnetic order are identified. The interplay between the various Ji j is revealed as a function of a in the framework of the corresponding magnetic phase diagrams.

  6. Stochastic kinetics of photoinduced phase transitions in spin-crossover solids

    Science.gov (United States)

    Gudyma, Iurii; Maksymov, Artur; Dimian, Mihai

    2013-10-01

    We study the stochastic macroscopic kinetics of photoinduced phase transitions in spin-crossover compounds assisted by white and colored Ornstein-Uhlenbeck noise. By using a phenomenological master equation obtained in the mean-field approach, the phase diagram is constructed based on the associated Lyapunov function. The stochastic behavior is then analyzed in the Langevin framework and the corresponding Fokker-Planck equations. Both additive and multiplicative and white and colored types of noise are considered and the stationary probability densities are found along with the noise-assisted light induced hysteretic loops. By using the Kramers formalism, we also focus our attention on the escape time problem in these noise perturbed systems. A detailed study of the relative escape time dependence on various noise characteristics is performed and the main features are compared for different types of noise.

  7. Stochastic kinetics of photoinduced phase transitions in spin-crossover solids.

    Science.gov (United States)

    Gudyma, Iurii; Maksymov, Artur; Dimian, Mihai

    2013-10-01

    We study the stochastic macroscopic kinetics of photoinduced phase transitions in spin-crossover compounds assisted by white and colored Ornstein-Uhlenbeck noise. By using a phenomenological master equation obtained in the mean-field approach, the phase diagram is constructed based on the associated Lyapunov function. The stochastic behavior is then analyzed in the Langevin framework and the corresponding Fokker-Planck equations. Both additive and multiplicative and white and colored types of noise are considered and the stationary probability densities are found along with the noise-assisted light induced hysteretic loops. By using the Kramers formalism, we also focus our attention on the escape time problem in these noise perturbed systems. A detailed study of the relative escape time dependence on various noise characteristics is performed and the main features are compared for different types of noise.

  8. Magnetic relaxation in a spin-1 Ising model near the second-order phase transition point

    Energy Technology Data Exchange (ETDEWEB)

    Erdem, Riza [Department of Physics, Gaziosmanpasa University, Tasliciftlik Campus, Tokat 60250 (Turkey)], E-mail: rerdem29@hotmail.com

    2008-09-15

    The magnetic relaxation of a spin-1 Ising model with bilinear and biquadratic interactions is formulated within the framework of statistical equilibrium theory and the thermodynamics of irreversible processes. Using a molecular-field expression for the magnetic Gibbs energy, the magnetic Gibbs energy produced in the irreversible process is calculated and time derivatives of the dipolar and quadrupolar order parameters are treated as fluxes conjugate to their appropriate generalized forces in the sense of Onsager theory. The kinetic equations are obtained by introducing kinetic coefficients that satisfy the Onsager relation. By solving these equations an expression is derived for the dynamic or complex magnetic susceptibility. From the real and imaginary parts of this expression, magnetic dispersion and absorption factor are calculated and analyzed near the second-order phase transition.

  9. Magnetic relaxation in a spin-1 Ising model near the second-order phase transition point

    Science.gov (United States)

    Erdem, Rıza

    The magnetic relaxation of a spin-1 Ising model with bilinear and biquadratic interactions is formulated within the framework of statistical equilibrium theory and the thermodynamics of irreversible processes. Using a molecular-field expression for the magnetic Gibbs energy, the magnetic Gibbs energy produced in the irreversible process is calculated and time derivatives of the dipolar and quadrupolar order parameters are treated as fluxes conjugate to their appropriate generalized forces in the sense of Onsager theory. The kinetic equations are obtained by introducing kinetic coefficients that satisfy the Onsager relation. By solving these equations an expression is derived for the dynamic or complex magnetic susceptibility. From the real and imaginary parts of this expression, magnetic dispersion and absorption factor are calculated and analyzed near the second-order phase transition.

  10. New mechanism of the spin-reorientation phase transition in neodymium orthochromite

    Energy Technology Data Exchange (ETDEWEB)

    Artem`ev, G.G. [Moscow State University, Moscow (Russian Federation); Kadomtseva, A.M. [Moscow State University, Moscow (Russian Federation); Milov, V.N. [Moscow State University, Moscow (Russian Federation); Lukina, M.M. [Moscow State University, Moscow (Russian Federation); Mukhin, A.A. [Institute of General Physics, 38 Vavilov st., 117942, Moscow (Russian Federation)

    1995-02-09

    Using magnetization and magnetostriction measurements we have investigated various field-induced and spontaneous spin-reorientation phase transitions (SRPT) in pure NdCrO{sub 3} and Nd{sub 1-x}Eu{sub x}CrO{sub 3} (x=0, 0.3, 0.5, 0.9) single crystals. Analysis of these data gives evidence that spontaneous Morin type {Gamma}{sub 2}(G{sub z}F{sub x})-{Gamma}{sub 1}(G{sub y}) SRPT in Nd{sub 1-x}Eu{sub x}CrO{sub 3} is determined by a competition between two contributions (Zeeman-like and Van Vleck) in the bc-plane anisotropy energy resulting from an anisotropic Nd-Cr exchange. ((orig.)).

  11. Spin Electronics

    Science.gov (United States)

    2003-08-01

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

  12. Dimensionality-Driven Metal-Insulator Transition in Spin-Orbit-Coupled SrIrO3

    NARCIS (Netherlands)

    Schütz, P.; Di Sante, D.; Dudy, L.; Gabel, J.; Stübinger, M.; Kamp, M.; Huang, Y.; Capone, M.; Husanu, M.A.; Strocov, V.N.; Sangiovanni, G.; Sing, M.; Claessen, R.

    2017-01-01

    Upon reduction of the film thickness we observe a metal-insulator transition in epitaxially stabilized, spin-orbit-coupled SrIrO3 ultrathin films. By comparison of the experimental electronic dispersions with density functional theory at various levels of complexity we identify the leading

  13. Area law violations and quantum phase transitions in modified Motzkin walk spin chains

    Science.gov (United States)

    Sugino, Fumihiko; Padmanabhan, Pramod

    2018-01-01

    Area law violations for entanglement entropy in the form of a square root have recently been studied for one-dimensional frustration-free quantum systems based on the Motzkin walks and their variations. Here we consider a Motzkin walk with a different Hilbert space on each step of the walk spanned by the elements of a symmetric inverse semigroup with the direction of each step governed by its algebraic structure. This change alters the number of paths allowed in the Motzkin walk and introduces a ground state degeneracy that is sensitive to boundary perturbations. We study the frustration-free spin chains based on three symmetric inverse semigroups, \

  14. Climate change, human health, and epidemiological transition.

    Science.gov (United States)

    Barrett, Bruce; Charles, Joel W; Temte, Jonathan L

    2015-01-01

    The health of populations depends on the availability of clean air, water, food, and sanitation, exposure to pathogens, toxins and environmental hazards, and numerous genetic, behavioral and social factors. For many thousands of years, human life expectancy was low, and population growth was slow. The development of technology-based civilizations facilitated what Abdel Omran called "epidemiological transition," with increasing life expectancy and rapid population growth. To a large extent, the spectacular growth of human populations during the past two centuries was made possible by the energy extracted from fossil fuels. We have now learned, however, that greenhouse gases from fossil fuel combustion are warming the planet's surface, causing changes in oceanic and atmospheric systems, and disrupting weather and hydrological patterns. Climate change poses unprecedented threats to human health by impacts on food and water security, heat waves and droughts, violent storms, infectious disease, and rising sea levels. Whether or not humanity can reduce greenhouse gas emissions quickly enough to slow climate change to a rate that will allow societies to successfully adapt is not yet known. This essay reviews the current state of relevant knowledge, and points in a few directions that those interested in human health may wish to consider. Copyright © 2014 Elsevier Inc. All rights reserved.

  15. Nd-induced Mn spin-reorientation transition in NdMnAsO

    Science.gov (United States)

    Marcinkova, A.; Hansen, T. C.; Curfs, C.; Margadonna, S.; Bos, J.-W. G.

    2010-11-01

    A combination of synchrotron x-ray, neutron powder-diffraction, magnetization, heat-capacity, and electrical-resistivity measurements reveals that NdMnAsO is an antiferromagnetic semiconductor with large Neel temperature [TN=359(2)K] . At room temperature the magnetic propagation vector k=0 and the Mn moments are directed along the crystallographic c axis [mMn=2.41(6)μB] . Upon cooling a spin-reorientation (SR) transition of the Mn moments into the ab plane occurs (TSR=23K) . This coincides with the long-range ordering of the Nd moments, which are restricted to the basal plane. The magnetic propagation vector remains k=0 . At base temperature (1.6 K) the fitted moments are mab,Mn=3.72(1)μB and mab,Nd=1.94(1)μB . The electrical resistivity is characterized by a broad maximum at 250 K, below which it has a metallic temperature dependence but semiconducting magnitude ( ρ250K=50Ωcm , residual resistivity ratio=2 ), and a slight upturn at the SR transition.

  16. Spin transitions in La{sub 0.7} Ba{sub 0.3}CoO{sub 3} thin films revealed by combining Raman spectroscopy and X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Othmen, Zied; Oueslati, Meherzi [Unité Nanomatériaux et Photonique, Faculty of Sciences of Tunis, Tunis El-Manar University, 2092 Tunis (Tunisia); Copie, Olivier; Gemeiner, Pascale; Dkhil, Brahim [Laboratoire Structures, Propriétés et Modélisation des Solides, Centrale Supélec, CNRS-UMR 8580, Université Paris-Saclay (France); Daoudi, Kais [Unité Nanomatériaux et Photonique, Faculty of Sciences of Tunis, Tunis El-Manar University, 2092 Tunis (Tunisia); Department of Applied Physics and Astronomy, College of Sciences, University of Sharjah, P.O. Box 27272, Sharjah (United Arab Emirates); Boudard, Michel [Univ. Grenoble Alpes, LMGP, F-38000 Grenoble (France)

    2016-07-07

    In cobaltite, the spin states transitions of Co{sup 3+/4+} ions govern the magnetic and electronic conduction properties. These transitions are strain-sensitive and can be varied using external parameters, including temperature, hydrostatic pressure, or chemical stresses through ionic substitutions. In this work, using temperature dependent Raman spectroscopy and X-ray diffraction, the epitaxial strain effects on both structural and vibrational properties of La{sub 0.7} Ba{sub 0.3} CoO{sub 3} (LBCO) cobaltite thin films are investigated. All Raman active phonon modes as well as the structure are found to be strongly affected. Both Raman modes and lattice parameter evolutions show temperature changes correlated with magnetic and electronic transitions properties. Combining Raman spectroscopy and X-ray diffraction appears as a powerful approach to probe the spin transition in thin film cobaltite. Our results provide insight into strong spin-charge-phonon coupling in LBCO thin film. This coupling manifests as vibrational transition with temperature in the Raman spectra near the ferromagnetic spin ordered transition at 220 K.

  17. Enhanced cooperative interactions at the nanoscale in spin-crossover materials with a first-order phase transition.

    Science.gov (United States)

    Félix, Gautier; Nicolazzi, William; Salmon, Lionel; Molnár, Gábor; Perrier, Marine; Maurin, Guillaume; Larionova, Joulia; Long, Jérôme; Guari, Yannick; Bousseksou, Azzedine

    2013-06-07

    We analyzed the size effect on a first-order spin transition governed by elastic interactions. This study was performed in the framework of a nonextensive thermodynamic core-shell model. When decreasing the particle size, differences in surface energies between the two phases lead to the shrinking of the thermal hysteresis width, the lowering of the transition temperature, and the increase of residual fractions at low temperature, in good agreement with recent experimental observations on spin transition nanomaterials. On the other hand, a modification of the particle-matrix interface may allow for the existence of the hysteresis loop even at very low sizes. In addition, an unexpected reopening of the hysteresis, when the size decreases, is also possible due to the hardening of the nanoparticles at very small sizes, which we deduced from the size dependence of the Debye temperature of a series of coordination nanoparticles.

  18. Enhanced Cooperative Interactions at the Nanoscale in Spin-Crossover Materials with a First-Order Phase Transition

    Science.gov (United States)

    Félix, Gautier; Nicolazzi, William; Salmon, Lionel; Molnár, Gábor; Perrier, Marine; Maurin, Guillaume; Larionova, Joulia; Long, Jérôme; Guari, Yannick; Bousseksou, Azzedine

    2013-06-01

    We analyzed the size effect on a first-order spin transition governed by elastic interactions. This study was performed in the framework of a nonextensive thermodynamic core-shell model. When decreasing the particle size, differences in surface energies between the two phases lead to the shrinking of the thermal hysteresis width, the lowering of the transition temperature, and the increase of residual fractions at low temperature, in good agreement with recent experimental observations on spin transition nanomaterials. On the other hand, a modification of the particle-matrix interface may allow for the existence of the hysteresis loop even at very low sizes. In addition, an unexpected reopening of the hysteresis, when the size decreases, is also possible due to the hardening of the nanoparticles at very small sizes, which we deduced from the size dependence of the Debye temperature of a series of coordination nanoparticles.

  19. Magnetization compensation and spin reorientation transition in ferrimagnetic DyCo5: Multiscale modeling and element-specific measurements

    Science.gov (United States)

    Donges, Andreas; Khmelevskyi, Sergii; Deak, Andras; Abrudan, Radu-Marius; Schmitz, Detlef; Radu, Ilie; Radu, Florin; Szunyogh, László; Nowak, Ulrich

    2017-07-01

    We use a multiscale approach linking ab initio calculations for the parametrization of an atomistic spin model with spin dynamics simulations based on the stochastic Landau-Lifshitz-Gilbert equation to investigate the thermal magnetic properties of the ferrimagnetic rare-earth transition-metal intermetallic DyCo5. Our theoretical findings are compared to elemental resolved measurements on DyCo5 thin films using the x-ray magnetic circular dichroism technique. With our model, we are able to accurately compute the complex temperature dependence of the magnetization. The simulations yield a Curie temperature of TC=1030 K and a compensation point of Tcomp=164 K , which is in a good agreement with our experimental result of Tcomp=120 K . The spin reorientation transition is a consequence of competing elemental magnetocrystalline anisotropies in connection with different degrees of thermal demagnetization in the Dy and Co sublattices. Experimentally, we find this spin reorientation in a region from TSR 1 ,2=320 to 360 K , whereas in our simulations the Co anisotropy appears to be underestimated, shifting the spin reorientation to higher temperatures.

  20. From non-linear magnetoacoustics and spin reorientation transition to magnetoelectric micro/nano-systems

    Science.gov (United States)

    Tiercelin, Nicolas; Preobrazhensky, Vladimir; BouMatar, Olivier; Talbi, Abdelkrim; Giordano, Stefano; Dusch, Yannick; Klimov, Alexey; Mathurin, Théo.; Elmazria, Omar; Hehn, Michel; Pernod, Philippe

    2017-09-01

    The interaction of a strongly nonlinear spin system with a crystalline lattice through magnetoelastic coupling results in significant modifications of the acoustic properties of magnetic materials, especially in the vicinity of magnetic instabilities associated with the spin-reorientation transition (SRT). The magnetoelastic coupling transfers the critical properties of the magnetic subsystem to the elastic one, which leads to a strong decrease of the sound velocity in the vicinity of the SRT, and allows a large control over acoustic nonlinearities. The general principles of the non-linear magneto-acoustics (NMA) will be introduced and illustrated in `bulk' applications such as acoustic wave phase conjugation, multi-phonon coupling, explosive instability of magneto-elastic vibrations, etc. The concept of the SRT coupled to magnetoelastic interaction has been transferred into nanostructured magnetoelastic multilayers with uni-axial anisotropy. The high sensitivity and the non-linear properties have been demonstrated in cantilever type actuators, and phenomena such as magneto-mechanical RF demodulation have been observed. The combination of the magnetic layers with piezoelectric materials also led to stress-mediated magnetoelectric (ME) composites with high ME coefficients, thanks to the SRT. The magnetoacoustic effects of the SRT have also been studied for surface acoustic waves propagating in the magnetoelastic layers and found to be promising for highly sensitive magnetic field sensors working at room temperature. On the other hand, mechanical stress is a very efficient way to control the magnetic subsystem. The principle of a very energy efficient stress-mediated magnetoelectric writing and reading in a magnetic memory is described.

  1. Energetics of the spin-state transition in LaCoO3: Total energy calculations using DFT +DMFT

    Science.gov (United States)

    Nanguneri, Ravindra; Park, Hyowon

    In this talk, we will present the energetics of the spin-state transition in strongly correlated LaCoO3 by adopting total energy calculations within density functional theory plus dynamical mean field theory (DFT +DMFT). We computed total energy curves as a function of volume for different spin states including low spin (LS), high spin (HS), and 1:1 mixed HS-LS states. We will show that as the volume is expanded, the mixed HS-LS state becomes energetically stable with a reasonable energy gap to the ground-state LS state. The nature of the HS-LS state is a paramagnetic insulator consistent with experiment while the homogeneous HS state is energetically much higher compared to the LS state. To analyze the dynamical fluctuation effect on the energetics, we also computed DFT +U energy curves by adopting the maximally localized Wannier function as correlated orbitals, same as used in DFT +DMFT calculations. The static correlation effect treated in DFT +U overestimates the tendency to higher spin states and the mixed spin state is wrongly predicted to be the ground state. The effect of the Coulomb interaction U, the Hund's coupling J, and the double counting potential on the energetics will be also discussed.

  2. Identification of ground-state spin ordering in antiferromagnetic transition metal oxides using the Ising model and a genetic algorithm.

    Science.gov (United States)

    Lee, Kyuhyun; Youn, Yong; Han, Seungwu

    2017-01-01

    We identify ground-state collinear spin ordering in various antiferromagnetic transition metal oxides by constructing the Ising model from first-principles results and applying a genetic algorithm to find its minimum energy state. The present method can correctly reproduce the ground state of well-known antiferromagnetic oxides such as NiO, Fe2O3, Cr2O3 and MnO2. Furthermore, we identify the ground-state spin ordering in more complicated materials such as Mn3O4 and CoCr2O4.

  3. Spin filtering effect in colorimetric chemosensor L-based molecular devices modulated with different transition metal ions

    Energy Technology Data Exchange (ETDEWEB)

    Shi, F.V.; Lv, Y.Z. [School of Physics and Technology, University of Jinan, Jinan 250022 (China); Zhao, P., E-mail: ss_zhaop@ujn.edu.cn [School of Physics and Technology, University of Jinan, Jinan 250022 (China); Liu, D.S. [School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Department of Physics, Jining University, Jining 273155 (China)

    2017-05-15

    Based on the density functional theory in conjunction with the non-equilibrium Green's function formalism, we explore the effect of transition metal (Mn, Fe, Co, Ni) ions on the magnetic transport properties of a new synthesized colorimetric chemosensor L. The calculated results show that only Mn-L can present high-efficiency spin filtering effect, even at room temperature. The underlying mechanism is explained by the spin-resolved electron occupation number, transmission spectra, molecular projected self-consistent Hamiltonian orbitals and their spatial distribution.

  4. Interplay of Fe and Tm moments through the spin-reorientation transition in TmFe O3

    Science.gov (United States)

    Staub, U.; Rettig, L.; Bothschafter, E. M.; Windsor, Y. W.; Ramakrishnan, M.; Avula, S. R. V.; Dreiser, J.; Piamonteze, C.; Scagnoli, V.; Mukherjee, S.; Niedermayer, C.; Medarde, M.; Pomjakushina, E.

    2017-11-01

    X-ray magnetic circular dichroism (XMCD) and x-ray magnetic linear dichroism (XMLD) have been used to investigate the Fe magnetic response during the spin-reorientation transition (SRT) in TmFe O3 . Comparing the Fe XMLD results with neutron-diffraction and magnetization measurements on the same sample indicates that the SRT has an enhanced temperature range in the near surface region of approximately 82 to 120 K compared to approximately 82 to 92 K in bulk. This view is supported by complementary resonant soft x-ray-diffraction experiments at the Tm M5 edge. These measurements find an induced magnetic moment on the Tm sites, which is well described by a dipolar mean-field model originating from the Fe moments. Even though such a model can describe the 4 f response in the experiments, it is insufficient to describe the SRT even when considering a change in the 4 f anisotropy. Moreover, the results of the Fe XMCD show a different temperature evolution through the SRT, the interpretation of which is hampered by additional spectral shape changes of the XCMD signal.

  5. Microstructure for ferroelastic transitions from strain pseudo-spin clock models in two and three dimensions: a mean field analysis

    Energy Technology Data Exchange (ETDEWEB)

    Lookman, Turab [Los Alamos National Laboratory; Vasseur, Romain [ECOLE NORMALE SUPERIEURE

    2009-01-01

    We obtain the microstructure of ferroelastic transitions in two and three dimensions from the solution of their corresponding discrete pseudo-spin models. In two dimensions we consider two transitions each from the high symmetry square and triangle symmetries: square-to-rectangle (SR), square-to-oblique (SO), triangle-to-centered rectangle (TR) and triangle-to-oblique (TO). In three dimensions we study the corresponding spin model for the cubic to tetragonal transition. The Landau free energies for these transitions result in N+ I states clock models (Z{sub N}) with long range interactions and we derive mean-field self-consistency equations for the clock model Hamiltonians. The microstructures from the mean-field solutions of the models are very similar to those obtained from the original continuum models or Monte Carlo simulations on the spin models (in the SR case), illustrating that these discrete models capture the salient physics. The models, in the presence of disorder, provide the basis for the study of the strain glass phase observed in martensitic alloys.

  6. Proxemic Transitions: Designing Shape-Changing Furniture for Informal Meetings

    DEFF Research Database (Denmark)

    Grønbæk, Jens Emil; Korsgaard, Henrik; Petersen, Marianne Graves

    2017-01-01

    of informal meetings and design work with shape-changing furniture, we develop the notion of proxemic transitions. We present three design aspects of proxemic transitions: transition speed, step- wise reconfiguration, and situational flexibility. The design aspects focus on how to balance between physical...

  7. Transition Experiments: Exploring societal changes towards sustainability

    NARCIS (Netherlands)

    S.J.M. van den Bosch (Suzanne)

    2010-01-01

    textabstractThis PhD thesis presents the outcome of exploratory research on how transition experiments can be used as instruments to further sustainable development. A transition experiment is a specific type of innovation project that is aimed at exploring radically new ways to meet societal

  8. Quantum critical properties of a metallic spin-density-wave transition

    Science.gov (United States)

    Gerlach, Max H.; Schattner, Yoni; Berg, Erez; Trebst, Simon

    2017-01-01

    We report on numerically exact determinantal quantum Monte Carlo simulations of the onset of spin-density-wave (SDW) order in itinerant electron systems captured by a sign-problem-free two-dimensional lattice model. Extensive measurements of the SDW correlations in the vicinity of the phase transition reveal that the critical dynamics of the bosonic order parameter are well described by a dynamical critical exponent z =2 , consistent with Hertz-Millis theory, but are found to follow a finite-temperature dependence that does not fit the predicted behavior of the same theory. The presence of critical SDW fluctuations is found to have a strong impact on the fermionic quasiparticles, giving rise to a dome-shaped superconducting phase near the quantum critical point. In the superconducting state we find a gap function that has an opposite sign between the two bands of the model and is nearly constant along the Fermi surface of each band. Above the superconducting Tc, our numerical simulations reveal a nearly temperature and frequency independent self-energy causing a strong suppression of the low-energy quasiparticle weight in the vicinity of the hot spots on the Fermi surface. This indicates a clear breakdown of Fermi liquid theory around these points.

  9. High-field magnetic phase transitions and spin excitations in magnetoelectric LiNiPO4

    DEFF Research Database (Denmark)

    Toft-Petersen, Rasmus; Jensen, Jens; Jensen, Thomas Bagger Stibius

    2011-01-01

    The magnetically ordered phases and spin dynamics of magnetoelectric LiNiPO4 have been studied in fields up to 17.3 T along the c axis. Using neutron diffraction, we show that a previously proposed linearly polarized incommensurate (IC) structure exists only for temperatures just below the Neel...... temperature T-N. The ordered IC structure at the lowest temperatures is shown instead to be an elliptically polarized canted spiral for fields larger than 12 T. The transition between the two IC phases is of second order and takes place about 2 K below T-N. For mu H-0 > 16 T and temperatures below 10 K......, the spiral structure is found to lock in to a period of five crystallographic unit cells along the b axis. Based on the neutron-diffraction data, combined with detailed magnetization measurements along all three crystallographic axes, we establish the magnetic phase diagrams for fields up to 17.3 T along c...

  10. TRANSITIONAL JUSTICE AND DEMOCRATIC CHANGE: KEY CONCEPTS

    Directory of Open Access Journals (Sweden)

    ELENA ANDREEVSKA

    2013-05-01

    Full Text Available This Article proposes a genealogy of transitional justice and focuses on transitional justice as one of the key steps in peace building that needs to be taken to secure a stable democratic futureTransitional justice is a response to systematic or widespread violations of human rights. It seeks recognition for victims and promotion of possibilities for peace, reconciliation and democracy. The paper focuses on key concepts of transitional justice before addressing its traditional components: justice, reparation, truth and institutional reform. This Article meeting point on the transitional process in a society which has experienced a violent conflict and needs adequate mechanisms to deal with the legacies of the past in order to prevent future violence and cover the way for reconciliation and democratic consolidation. It provides key stakeholders with an overview of transitional justice and its different components, while examining key challenges faced by those working in this area. The present paper concludes with some remarks that challenge the traditional concept of transitional justice and its processes in order to initiate important debate on where future work in this field is needed.

  11. Consolidating Change: Transitional Security and Operational Art

    National Research Council Canada - National Science Library

    Boy, Donald S

    2006-01-01

    ... intervention repeated in later crises. Greater focus on certain core concepts such as security in a transitional environment would help to ensure both civilian and military leaders and planners share assumptions, definitions and desired end-states...

  12. Spin crossover and Mott—Hubbard transition under high pressure and high temperature in the low mantle of the Earth

    Science.gov (United States)

    Ovchinnikov, S. G.; Ovchinnikova, T. M.; Plotkin, V. V.; Dyad'kov, P. G.

    2015-11-01

    Effect of high pressure induced spin crossover on the magnetic, electronic and structural properties of the minerals forming the Earth's low mantle is discussed. The low temperature P, T phase diagram of ferropericlase has the quantum phase transition point Pc = 56 GPa at T = 0 confirmed recently by the synchrotron Mössbauer spectroscopy. The LDA+GTB calculated phase diagram describes the experimental data. Its extension to the high temperature resulted earlier in prediction of the metallic properties of the Earth's mantle at the depth 1400 km insulator transition and compare them with the experimental seismic and geomagnetic field data.

  13. Universities in Transition: The Changing Role and Challenges for ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Universities in Transition: The Changing Role and Challenges for Academic Institutions. Book cover Universities in Transition: The Changing Role and Challenges for Academic Institutions. Directeur(s) : Bo Göransson and Claes Brundenius. Maison(s) d'édition : Springer, IDRC. 1 janvier 2011. ISBN : 9781441975089.

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

    Indian Academy of Sciences (India)

    Abstract. We discuss the possibility of spin-glass order in the vicinity of the unexpected metallic state of the two-dimensional electron gas in zero applied magnetic field. An average ferromagnetic moment may also be present, and the spin-glass order then resides in the plane orthogonal to the ferromagnetic moment.

  15. Zero-momentum coupling induced transitions of ground states in Rashba spin-orbit coupled Bose-Einstein condensates

    Science.gov (United States)

    Jin, Jingjing; Zhang, Suying; Han, Wei

    2014-06-01

    We investigate the transitions of ground states induced by zero momentum (ZM) coupling in pseudospin-1/2 Rashba spin-orbit coupled Bose-Einstein condensates confined in a harmonic trap. In a weak harmonic trap, the condensate presents a plane wave (PW) state, a stripe state or a spin polarized ZM state, and the particle distribution of the stripe state is weighted equally at two points in the momentum space without ZM coupling. The presence of ZM coupling induces an imbalanced particle distribution in the momentum space, and leads to the decrease of the amplitude of the stripe state. When its strength exceeds a critical value, the system experiences the transition from stripe phase to PW phase. The boundary of these two phases is shifted and a new phase diagram spanned by the ZM coupling and the interatomic interactions is obtained. The presence of ZM coupling can also achieve the transition from ZM phase to PW phase. In a strong harmonic trap, the condensate exhibits a vortex lattice state without ZM coupling. For the positive effective Rabi frequency of ZM coupling, the condensate is driven from a vortex lattice state to a vortex-free lattice state and finally to a PW state with the increase of coupling strength. In addition, for the negative effective Rabi frequency, the condensate is driven from a vortex lattice state to a stripe state, and finally to a PW state. The stripe state found in the strong harmonic trap is different from that in previous works because of its nonzero superfluid velocity along the stripes. We also discuss the influences of the ZM coupling on the spin textures, and indicate that the spin textures are squeezed transversely by the ZM coupling.

  16. Phase Transitions in Spin-Crossover Thin Films Probed by Graphene Transport Measurements.

    Science.gov (United States)

    Dugay, J; Aarts, M; Giménez-Marqués, M; Kozlova, T; Zandbergen, H W; Coronado, E; van der Zant, H S J

    2017-01-11

    Future multifunctional hybrid devices might combine switchable molecules and 2D material-based devices. Spin-crossover compounds are of particular interest in this context since they exhibit bistability and memory effects at room temperature while responding to numerous external stimuli. Atomically thin 2D materials such as graphene attract a lot of attention for their fascinating electrical, optical, and mechanical properties, but also for their reliability for room-temperature operations. Here, we demonstrate that thermally induced spin-state switching of spin-crossover nanoparticle thin films can be monitored through the electrical transport properties of graphene lying underneath the films. Model calculations indicate that the charge carrier scattering mechanism in graphene is sensitive to the spin-state dependence of the relative dielectric constants of the spin-crossover nanoparticles. This graphene sensor approach can be applied to a wide class of (molecular) systems with tunable electronic polarizabilities.

  17. Quantum phase transitions in strained graphene due to the interplay between spin fluctuations and anisotropic band structure

    Science.gov (United States)

    Arya, S.; Laad, M. S.; Hassan, S. R.

    2017-08-01

    Strain tuning is increasingly being recognized as a clean tuning parameter to induce novel behavior in quantum matter. Motivated by the possibility of straining graphene up to 20 percent, we investigate novel quantum criticality due to interplay between strain-induced anisotropic band structure and critical antiferromagnetic (AF) spin fluctuations in this setting. We detail how this interplay drives (i) a quantum phase transition (QPT) between the Dirac-semimetal-incoherent pseudogapped metal-correlated insulator as a function of strain (ɛ ), and (ii) critical AF spin fluctuations-driven divergent nematic susceptibility near critical strain (ɛc) manifesting as critical singularities in magnetothermal expansion and Grüneisen coefficients. The correlated band insulator at large strain affords realization of a two-dimensional dimerized spin-singlet state due to this interplay, and doping such an insulator can lead to a spin-charge separated metal, leading to anomalous metallicity and possible unconventional superconductivity. On a wider front, our work serves to illustrate the range of novel states realizable by strain-tuning quantum materials.

  18. Theory of relaxation phenomena in a spin-3/2 Ising system near the second-order phase transition temperature

    Energy Technology Data Exchange (ETDEWEB)

    Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)]. E-mail: keskin@erciyes.edu.tr; Canko, Osman [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2005-12-19

    The relaxation behavior of the spin-3/2 Ising model Hamiltonian with bilinear and biquadratic interactions near the second-order phase transition temperature or critical temperature is studied by means of the Onsager's theory of irreversible thermodynamics or the Onsager reciprocity theorem (ORT). First, we give the equilibrium case briefly within the molecular-field approximation in order to study the relaxation behavior by using the ORT. Then, the ORT is applied to the model and the kinetic equations are obtained. By solving these equations, three relaxation times are calculated and examined for temperatures near the second-order phase transition temperature. It is found that one of the relaxation times goes to infinity near the critical temperature on either side, the second relaxation time makes a cusp at the critical temperature and third one behaves very differently in which it terminates at the critical temperature while approaching it, then showing a 'flatness' property and then decreases. We also study the influences of the Onsager rate coefficients on the relaxation times. The behavior of these relaxation times is discussed and compared with the spin-1/2 and spin-1 Ising systems.

  19. Theory of relaxation phenomena in a spin-3/2 Ising system near the second-order phase transition temperature

    Science.gov (United States)

    Keskin, Mustafa; Canko, Osman

    2005-12-01

    The relaxation behavior of the spin-3/2 Ising model Hamiltonian with bilinear and biquadratic interactions near the second-order phase transition temperature or critical temperature is studied by means of the Onsager's theory of irreversible thermodynamics or the Onsager reciprocity theorem (ORT). First, we give the equilibrium case briefly within the molecular-field approximation in order to study the relaxation behavior by using the ORT. Then, the ORT is applied to the model and the kinetic equations are obtained. By solving these equations, three relaxation times are calculated and examined for temperatures near the second-order phase transition temperature. It is found that one of the relaxation times goes to infinity near the critical temperature on either side, the second relaxation time makes a cusp at the critical temperature and third one behaves very differently in which it terminates at the critical temperature while approaching it, then showing a “flatness” property and then decreases. We also study the influences of the Onsager rate coefficients on the relaxation times. The behavior of these relaxation times is discussed and compared with the spin-1/2 and spin-1 Ising systems.

  20. Doping induced spin state transition in LaCoO3: dynamical mean-field study.

    Science.gov (United States)

    Augustinský, P; Křápek, V; Kuneš, J

    2013-06-28

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

  1. Structural changes induced spin-reorientation of ultrathin Mn films grown on Ag(001)

    Energy Technology Data Exchange (ETDEWEB)

    Ouarab, N., E-mail: ouarab_nourdine@yahoo.fr [Quantum Physics and Dynamical Systems Laboratory, Ferhat Abbas University of Sétif (Algeria); Semiconductor Technology Research Center for Energetic-(CRTSE), 02, Bd Frantz Fanon Algiers, BP N° 140 (Algeria); Haroun, A. [Quantum Physics and Dynamical Systems Laboratory, Ferhat Abbas University of Sétif (Algeria); Baadji, N. [School of Physics and CRANN, Trinity College, Dublin 2 (Ireland)

    2016-12-01

    The strained body centered tetragonal (bct) Mn ultrathin film from lattice parameter a=2.89 Å to lattice value of 2.73 Å induces anti-ferromagnetic behavior between Mn layers. The magnetic easy axis of Mn film was demonstrated theoretically to switch from the in-plane to out-of-plane by magneto-optical Kerr effect investigation. By including spin–orbit coupling in full potential linearized augmented plane waves and linearized muffin-tin orbitals methods, manganese ultrathin film displays different magnetic behaviors and the spin-reorientation transition is shown to be correlated to these structural changes. The calculated magnetic moment of manganese planes are enhanced and reach a value of ~4.02 μ{sub B}. The polar magneto-optical Kerr effect is calculated for a photon energy range extended to 15 eV. It shows a pronounced peak in visible light. - Highlights: • The applied strain in Mn-bct structure induces anti-ferromagnetic behavior. • The easy magnetization axis is demonstrated to be out-of-plane. • The magnetic moment of Mn-layers are enhanced and reach a value of ~4.02 μ{sub B}. • Kerr spectra show significant polar responses for Mn films in the visible range. • The prominent structures in the Kerr spectra have been identified.

  2. Time-dependent spin and charge transport in Floquet topological insulator based on graphene nanoribbons with proximity induced spin-orbit coupling from transition metal dichalcogenides

    Science.gov (United States)

    Popescu, Bogdan; Chen, Son-Hsien; Nikolic, Branislav

    The investigation of time-resolved phenomena in nanodevices is a topical research subject. To this end, an efficient algorithm, based on time-dependent nonequilibrium Green's functions (TDNEGF) was recently developed in Ref.. This approach converts the TDNEGF equations into an initial-value problem for the reduced density matrix (RDO) and auxiliary quantities. Moreover, since the RDO is propagated, all information on dynamics is accessible at each time step without extra effort. In this study, we employ the algorithm of Ref. to investigate spin and charge transport in graphene nanoribbons (GNR), with proximity induced spin-orbit coupling (SOC) from transition metal dichalcogenides underneath the ribbon, which are irradiated by circularly polarized light and attached to Fermi liquid reservoirs via semi-infinite ideal GNR leads. The usage of such leads bypasses ambiguities in defining the nonequilibrium occupations of the Floquet states, while discretization of the lead self-energies by a fitting procedure describes the system-lead coupling as reflectionless. We also compare long-time limit of TDNEGF algorithm with Floquet-NEGF approach of Ref.. NSF Grant No. ECCS 1566074.

  3. Shape change as entropic phase transition: A study using Jarzynski ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 124; Issue 1. Shape change as entropic phase transition: A study using ... Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/jcsc/124/01/0021-0028. Keywords. Fick-Jacobs equation; entropic potental; Jarzynski equality; phase transition.

  4. 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.

  5. High-spin transition quadrupole moments in neutron-rich Mo and Ru nuclei: Testing γ softness?

    Energy Technology Data Exchange (ETDEWEB)

    Snyder, J.B. [Physics Department, Washington University, St. Louis, MO 63130 (United States); Reviol, W., E-mail: reviol@wustl.edu [Chemistry Department, Washington University, St. Louis, MO 63130 (United States); Sarantites, D.G. [Chemistry Department, Washington University, St. Louis, MO 63130 (United States); Afanasjev, A.V. [Department of Physics and Astronomy, Mississippi State University, Starkville, MS 39762 (United States); Janssens, R.V.F. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Abusara, H. [Department of Physics, Faculty of Science, An-Najah National University, Nablus, Palestine (Country Unknown); Carpenter, M.P. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Chen, X. [Chemistry Department, Washington University, St. Louis, MO 63130 (United States); Chiara, C.J. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742 (United States); Greene, J.P.; Lauritsen, T. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States); McCutchan, E.A. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States); National Nuclear Data Center, Brookhaven National Laboratory, Upton, NY 11973 (United States); Seweryniak, D.; Zhu, S. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States)

    2013-06-10

    The transition quadrupole moments, Q{sub t}, of rotational bands in the neutron-rich, even-mass {sup 102–108}Mo and {sup 108–112}Ru nuclei were measured in the 8–16 ℏ spin range with the Doppler-shift attenuation method. The nuclei were populated as fission fragments from {sup 252}Cf fission. The detector setup consisted of the Gammasphere spectrometer and the HERCULES fast-plastic array. At moderate spin, the Q{sub t} moments are found to be reduced with respect to the values near the ground states. Attempts to describe the observations in mean-field-based models, specifically cranked relativistic Hartree–Bogoliubov theory, illustrate the challenge theory faces and the difficulty to infer information on γ softness and triaxiality from the data.

  6. Ising Spin Network States for Loop Quantum Gravity: a Toy Model for Phase Transitions

    CERN Document Server

    Feller, Alexandre

    2015-01-01

    Non-perturbative approaches to quantum gravity call for a deep understanding of the emergence of geometry and locality from the quantum state of the gravitational field. Without background geometry, the notion of distance should entirely emerge from the correlations between the gravity fluctuations. In the context of loop quantum gravity, quantum states of geometry are defined as spin networks. These are graphs decorated with spin and intertwiners, which represent quantized excitations of areas and volumes of the space geometry. Here, we develop the condensed matter point of view on extracting the physical and geometrical information out of spin network states: we introduce new Ising spin network states, both in 2d on a square lattice and in 3d on a hexagonal lattice, whose correlations map onto the usual Ising model in statistical physics. We construct these states from the basic holonomy operators of loop gravity and derive a set of local Hamiltonian constraints which entirely characterize our states. We di...

  7. Modeling nonequilibrium dynamics of phase transitions at the nanoscale: Application to spin-crossover

    National Research Council Canada - National Science Library

    Park, Sang Tae; van der Veen, Renske M

    2017-01-01

    ... switching in individual spin-crossover nanoparticles, such as the thermal properties of the (graphite) substrate, the particle thickness, and the interfacial thermal contact conductance between the substrate and the nanoparticle...

  8. Spin state transition in LaCoO3 studied using soft x-ray absorption spectroscopy and magnetic circular dichroism.

    Science.gov (United States)

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

    2006-10-27

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

  9. Tensor order parameters for magnetic-structural phase transitions in crystals with strong spin-lattice coupling

    Science.gov (United States)

    Birman, Joseph L.; Izyumov, Yuri A.

    1980-02-01

    We formulate the thermodynamic theory of phase transitions in magnetically ordered systems in terms of a tensor, or coupled, order parameter. This basis is constructed by coupling atomic spin and lattice displacement. Symmetry lowering is predicted at the second-order phase transition point (tricritical points are not considered here). Lower-symmetry phases should in general be classified according to the Shubnikov symmetry space group Sh, which will reveal the total broken symmetry due to the coupled order parameter. In case the apparatus is "blind" to one portion of the order parameter: either spin or displacement, the apparent symmetry group will not be Sh, but a related space group, which will reveal "partial information." Comparing this formulation and the usual (uncoupled) theory, new results are obtained here: for example "pseudoscalar order parameters" can arise and different "symmetry-broken" groups. An illustration is given by applying the formulation to the spinel-structure space group: O7h-Fd3m. It is conjectured that for TbNi2 the tensor order parameter Γ1- may be relevant, so that the phase transition which has been identified as O7h-->Sh101166 may actually be O7h-->Sh132227, caused by a pseudoscalar.

  10. First- and second-order phase transitions between quantum and classical regimes for the escape rate of a biaxial spin system

    CERN Document Server

    Kim, G H

    1999-01-01

    The particle Hamiltonian for a biaxial spin system with a transverse or longitudinal magnetic field is investigated. We apply the Hamiltonian to the quantum-classical escape rate transition in small magnets. It is found that the phase boundary separating the first- and second-order transition is greatly influenced by the transverse anisotropy constant as well as the external magnetic field.

  11. Light-induced magnetization changes in a coordination polymer heterostructure of a Prussian blue analogue and a Hofmann-like Fe(II) spin crossover compound.

    Science.gov (United States)

    Gros, Corey R; Peprah, Marcus K; Hosterman, Brian D; Brinzari, Tatiana V; Quintero, Pedro A; Sendova, Mariana; Meisel, Mark W; Talham, Daniel R

    2014-07-16

    Coordination polymer thin film heterostructures of the Prussian blue analogue Ni(II)b[Cr(III)(CN)6](0.7)·nH2O (NiCr-PBA) and the 3D Hofmann-like spin crossover compound Fe(azpy)[Pt(CN)4]·xH2O {azpy = 4,4'-azopyridine} have been developed, and spin transition properties have been characterized via SQUID magnetometry and Raman spectroscopy. The magnetic response of the ferromagnetic NiCr-PBA layer (T(c) ≈ 70 K) can be altered by inducing the LIESST effect (light-induced excited spin state trapping) in the coupled paramagnetic Fe(II) spin crossover material. Whereas an increase in magnetization is measured for the single-phase Fe(azpy)[Pt(CN)4]·xH2O, a decrease in magnetization is observed for the heterostructure. These results indicate the LIESST effect alone cannot account for the sign and magnitude of the magnetization change in the heterostructure, but the temperature profile of the magnetization shows that significant changes in the NiCr-PBA network are correlated to the spin state of the Hofmann-like SCO network.

  12. The Changing Nature of Doing Business in Transition Economies

    DEFF Research Database (Denmark)

    The Changing Nature of Doing Business in Transition Economies uses a variety of national backgrounds to review the advancing business development of emerging economies and the impact of changing business conditions. It provides detailed insights into the way in which businesses function successfu......The Changing Nature of Doing Business in Transition Economies uses a variety of national backgrounds to review the advancing business development of emerging economies and the impact of changing business conditions. It provides detailed insights into the way in which businesses function...

  13. Phase transition in the PT-symmetric spin-1/2 quantum chain

    Science.gov (United States)

    Karnaukhov, Igor N.

    2012-11-01

    We study a PT-symmetric spin-1/2 chain in which spins are located at the vertices connected and exchange interact along links. The model presented has exact solution for arbitrary values of the exchange integrals. The ground-state phase diagram consists of two states with different static Z2 gauge fields; all Z2 charges are equal to +1 or -1. These states are separated by a quantum critical point ψc = π/4, ψc is a critical value of the phase, that defines the PT-symmetric exchange interactions of spins inside the cell. The single-particle spectrum of the Majorana fermions in the sectors with uniform fluxes is defined by flat-band fermion states at ψ = 0, π/2 and band states at 0 article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Quantum physics with non-Hermitian operators’.

  14. Entanglement and quantum phase transition in a mixed-spin Heisenberg chain with single-ion anisotropy

    Science.gov (United States)

    Solano-Carrillo, E.; Franco, R.; Silva-Valencia, J.

    2011-06-01

    We study the ground-state and thermal entanglement in the mixed-spin (S,s)=(1,1/2) Heisenberg chain with single-ion anisotropy D using exact diagonalization of small clusters. In this system, a quantum phase transition is revealed to occur at the value D=0, which is the bifurcation point for the global ground state; that is, when the single-ion anisotropy energy is positive, the ground state is unique, whereas when it is negative, the ground state becomes doubly degenerate and the system has the ferrimagnetic long-range order. Using the negativity as a measure of entanglement, we find that a pronounced dip in this quantity, taking place just at the bifurcation point, serves to signal the quantum phase transition. Moreover, we show that the single-ion anisotropy helps to improve the characteristic temperatures above which the quantum behavior disappears.

  15. Strong electron-hole symmetric Rashba spin-orbit coupling in graphene/monolayer transition metal dichalcogenide heterostructures

    Science.gov (United States)

    Yang, Bowen; Lohmann, Mark; Barroso, David; Liao, Ingrid; Lin, Zhisheng; Liu, Yawen; Bartels, Ludwig; Watanabe, Kenji; Taniguchi, Takashi; Shi, Jing

    2017-07-01

    Despite its extremely weak intrinsic spin-orbit coupling (SOC), graphene has been shown to acquire considerable SOC by proximity coupling with exfoliated transition metal dichalcogenides (TMDs). Here we demonstrate strong induced Rashba SOC in graphene that is proximity coupled to a monolayer TMD film, Mo S2 or WS e2 , grown by chemical-vapor deposition with drastically different Fermi level positions. Graphene/TMD heterostructures are fabricated with a pickup-transfer technique utilizing hexagonal boron nitride, which serves as a flat template to promote intimate contact and therefore a strong interfacial interaction between TMD and graphene as evidenced by quenching of the TMD photoluminescence. We observe strong induced graphene SOC that manifests itself in a pronounced weak-antilocalization (WAL) effect in the graphene magnetoconductance. The spin-relaxation rate extracted from the WAL analysis varies linearly with the momentum scattering time and is independent of the carrier type. This indicates a dominantly Dyakonov-Perel spin-relaxation mechanism caused by the induced Rashba SOC. Our analysis yields a Rashba SOC energy of ˜1.5 meV in graphene/WS e2 and ˜0.9 meV in graphene/Mo S2 . The nearly electron-hole symmetric nature of the induced Rashba SOC provides a clue to possible underlying SOC mechanisms.

  16. Spin filtering in transition-metal phthalocyanine molecules from first principles

    Science.gov (United States)

    Niu, Li; Wang, Huan; Bai, Lina; Rong, Ximing; Liu, Xiaojie; Li, Hua; Yin, Haitao

    2017-08-01

    Using first-principles calculations based on density functional theory and the nonequilibrium Green's function formalism, we studied the spin transport through metal-phthalocyanine (MPc, M=Ni, Fe, Co, Mn, Cr) molecules connected to aurum nanowire electrodes. We found that the MnPc, FePc, and CrPc molecular devices exhibit a perfect spin filtering effect compared to CoPc and NiPc. Moreover, negative differential resistance appears in FePc molecular devices. The transmission coefficients at different bias voltages were further presented to understand this phenomenon. These results would be useful in designing devices for future nanotechnology.

  17. On the origin of multi-step spin transition behaviour in 1D nanoparticles

    Science.gov (United States)

    Chiruta, Daniel; Jureschi, Catalin-Maricel; Linares, Jorge; Dahoo, Pierre Richard; Garcia, Yann; Rotaru, Aurelian

    2015-09-01

    To investigate the spin state switching mechanism in spin crossover (SCO) nanoparticles, a special attention is given to three-step thermally induced SCO behavior in 1D chains. An additional term is included in the standard Ising-like Hamiltonian to account for the border interaction between SCO molecules and its local environment. It is shown that this additional interaction, together with the short range interaction, drives the multi-steps thermal hysteretic behavior in 1D SCO systems. The relation between a polymeric matrix and this particular multi-step SCO phenomenon is discussed accordingly. Finally, the environmental influence on the SCO system's size is analyzed as well.

  18. Spin Transition of Iron and Crystal Structure in FeO from X-ray Emission Spectroscopy and Diffraction Measurements

    Science.gov (United States)

    Ozawa, H.; Hirose, K.; Ishii, H.; Hiraoka, N.; Ohishi, Y.

    2010-12-01

    FeO is definitely an important component in the Earth’s core because of high oxygen solubility into liquid iron at high pressure. High-pressure behavior of FeO is, therefore, of our great interest to geophysics. However, phase relationships in FeO at high pressure and high temperature still remain controversial, which is mainly due to lack of information on magnetic state of iron. The spin state of iron in FeO has been experimentally investigated by Mössbauer spectroscopy and X-ray emission spectroscopy (XES) to Mbar pressures [Pasternak et al., 1997 PRL; Badro et al., 1999 PRL]. However, there is a discrepancy between these studies probably because of sluggish structural transition at room temperature from rhombohedral to NiAs-type (B8) in FeO. Here we examined the spin state of iron and the crystal structure in FeO with combination of XES and X-ray diffraction (XRD) measurements at SPring-8. Starting material was commercially available Fe0.95O powder. The high-pressure phases of FeO were synthesized at high pressure and high temperature using a laser-heated diamond-anvil cell and examined by in-situ XRD measurements. XES spectra of the Fe Kβ fluorescence lines were collected up to 146 GPa. At 36 GPa, FeO with rhombohedral structure shows high-spin state, which is consistent with the previous studies. The satellite peak Kβ’ of iron in B8 phase completely disappeared at 146 GPa, indicating the loss of the 3d magnetic moment. We further collected XES spectra at 119 and 103 GPa with decreasing pressure. The presence of the Kβ’ peak of iron in B8 phase was clearly observed at 103 GPa whereas it was absent at 119 GPa, which suggests that the spin collapse occurred between these pressures. Furthermore, the volume measurements of B8 phase were conducted at P=77-132 GPa and 88-139 GPa at T=300 K and 1500-1700 K, respectively, using in-situ XRD. Sharp density discontinuity was observed at around 120 GPa at both 300 K and 1500-1700 K, which is most likely

  19. Diversity of quantum ground states and quantum phase transitions of a spin-1/2 Heisenberg octahedral chain

    Science.gov (United States)

    Strečka, Jozef; Richter, Johannes; Derzhko, Oleg; Verkholyak, Taras; Karľová, Katarína

    2017-06-01

    The spin-1/2 Heisenberg octahedral chain with regularly alternating monomeric and square-plaquette sites is investigated using various analytical and numerical methods: variational technique, localized-magnon approach, exact diagonalization (ED), and density-matrix renormalization group (DMRG) methods. The model belongs to the class of flatband systems and it has a rich ground-state phase diagram including phases with spontaneously broken translational symmetry. Moreover, it exhibits an anomalous low-temperature thermodynamics close to continuous or discontinuous field-driven quantum phase transitions between three quantum ferrimagnetic phases, tetramer-hexamer phase, monomer-tetramer phase, localized-magnon phase, and two different spin-liquid phases. If the intraplaquette coupling is at least twice as strong as the monomer-plaquette coupling, the variational method furnishes a rigorous proof of the monomer-tetramer ground state in a low-field region and the localized-magnon approach provides exact evidence of a single magnon trapped at each square plaquette in a high-field region. In the rest of the parameter space we have numerically studied the ground-state phase diagram and magnetization process using DMRG and ED methods. It is shown that the zero-temperature magnetization curve may involve up to four intermediate plateaus at zero, one-fifth, two-fifths, and three-fifths of the saturation magnetization, while the specific heat exhibits a striking low-temperature peak in the vicinity of discontinuous quantum phase transitions.

  20. ELECTRONIC-STRUCTURE AND SPIN-STATE TRANSITION OF LACOO3

    NARCIS (Netherlands)

    ABBATE, M; FUGGLE, JC; FUJIMORI, A; TJENG, LH; CHEN, CT; POTZE, R; SAWATZKY, GA; EISAKI, H; UCHIDA, S

    1993-01-01

    We present soft-x-ray absorption spectra (XAS) of LaCoO3 taken at different temperatures (80-630 K). The shape of the multiplets in the Co 2p XAS spectra conveys information on the symmetry and spin of the ground state. The 0 Is XAS spectra are related to unoccupied metal bands through covalent

  1. Ferromagnetic transition in a one-dimensional spin-orbit-coupled metal and its mapping to a critical point in smectic liquid crystals

    Science.gov (United States)

    Kozii, Vladyslav; Ruhman, Jonathan; Fu, Liang; Radzihovsky, Leo

    2017-09-01

    We study the quantum phase transition between a paramagnetic and ferromagnetic metal in the presence of Rashba spin-orbit coupling in one dimension. Using bosonization, we analyze the transition by means of renormalization group, controlled by an ɛ expansion around the upper critical dimension of two. We show that the presence of Rashba spin-orbit coupling allows for a new nonlinear term in the bosonized action, which generically leads to a fluctuation driven first-order transition. We further demonstrate that the Euclidean action of this system maps onto a classical smectic-A-C phase transition in a magnetic field in two dimensions. We show that the smectic transition is second order and is controlled by a new critical point.

  2. Supramolecular spintronic devices: spin transitions and magnetostructural correlations in [Fe4IIL4]8+ [2x2]-grid-type complexes.

    Science.gov (United States)

    Ruben, Mario; Breuning, Esther; Lehn, Jean-Marie; Ksenofontov, Vadim; Renz, Franz; Gütlich, Philip; Vaughan, Gavin B M

    2003-09-22

    The magnetism of a series of tetranuclear complexes of the [Fe4IIL4]8+ [2x2]-grid-type was investigated, revealing the occurrence of spin transition behavior within this class of compounds. The phenomenon depends directly on the nature of the substituent R(1) in the 2-position on the central pyrimidine group of the ligand L. All Fe(II) ions in compounds with R(1) substituents favoring strong ligand fields (R(1)=H; OH) remain completely in the diamagnetic low-spin state. Only complexes bearing R(1) substituents attenuating the ligand field by steric (and to a lesser extent electronic) effects (R(1)=Me; Ph) exhibit spin transition behavior triggered by temperature. In general, gradual and incomplete transitions without hysteresis were observed for magnetically active complexes. The systems described provide approaches to the development of (supra)molecular spintronics.

  3. Novel cryogenic Penning trap for the detection of spin transitions of a proton and determination of its g-factor; Neuartige kryogene Penning-Falle fuer den Nachweis von Spin-Uebergaengen eines Protons und Bestimmung seines g-Faktors

    Energy Technology Data Exchange (ETDEWEB)

    Carvalho Rodegheri, Cricia de

    2014-07-31

    This thesis presents the design, development, commissioning and characterization of a novel Penning trap in the framework of the experiment for the direct Determination of the g-factor of a single proton. This trap is distinguished by the fact that the field lines of an external homogeneous magnetic field are distorted around the trap Center by means of a ferromagnetic ring electrode. The inhomogeneous part of the resulting magnetic field, the so-called magnetic bottle, can be quantified by the the coefficient B{sub 2}=297(10) mT/mm{sup 2} of the second-order term in the series expansion describing the field. Such an exceptionally strong field inhomogeneity is a fundamental prerequisite for the detection of the proton spin orientation via the continuous Stern-Gerlach effect. This effect is based upon the coupling of the spin degree of freedom of the trapped proton to one of its eigenfrequencies, which occurs in the presence of the inhomogeneous magnetic field. Thus, a transition between the spin states can be detected as a frequency jump. The measurable change in frequency is proportional to B{sub 2} and to the in the case of the Proton extremely small ratio between its magnetic moment and its mass. The technical challenges due to the needed high magnetic inhomogeneity require a well-founded understanding and control of the the properties of the Penning trap and experimental conditions. The Penning trap developed in the present work allowed the first non-destructive detection of spin quantum jumps of a single trapped proton, which represented a breakthrough in the experiment for the direct determination of the g-factor with the aimed relative uncertainty of 10{sup -9}. By means of a statistical method the Larmor and the cyclotron frequency of the proton could be measured in the inhomogeneous magnetic field of the trap, from which the g-factor could be determined with a relative uncertainty of 8.9 x 10{sup -6}.The experimental techniques and setup presented here can

  4. Spontaneous Spin Bifurcations and Ferromagnetic Phase Transitions in a Spinor Exciton-Polariton Condensate

    Directory of Open Access Journals (Sweden)

    H. Ohadi

    2015-07-01

    Full Text Available We observe a spontaneous parity breaking bifurcation to a ferromagnetic state in a spatially trapped exciton-polariton condensate. At a critical bifurcation density under nonresonant excitation, the whole condensate spontaneously magnetizes and randomly adopts one of two elliptically polarized (up to 95% circularly polarized states with opposite handedness of polarization. The magnetized condensate remains stable for many seconds at 5 K, but at higher temperatures, it can flip from one magnetic orientation to another. We optically address these states and demonstrate the inversion of the magnetic state by resonantly injecting 100-fold weaker pulses of opposite spin. Theoretically, these phenomena can be well described as spontaneous symmetry breaking of the spin degree of freedom induced by different loss rates of the linear polarizations.

  5. Simulation of multi-steps thermal transition in 2D spin-crossover nanoparticles

    Science.gov (United States)

    Jureschi, Catalin-Maricel; Pottier, Benjamin-Louis; Linares, Jorge; Richard Dahoo, Pierre; Alayli, Yasser; Rotaru, Aurelian

    2016-04-01

    We have used an Ising like model to study the thermal behavior of a 2D spin crossover (SCO) system embedded in a matrix. The interaction parameter between edge SCO molecules and its local environment was included in the standard Ising like model as an additional term. The influence of the system's size and the ratio between the number of edge molecules and the other molecules were also discussed.

  6. Temperature phase transitions associated with local minima of energy in continous unbounded spins

    CERN Document Server

    Dobrovolny, B

    2004-01-01

    {\\footnotesize In this work we develop an alternative version of the theory of contour models adapted to continuous spins, $\\omega_{x}\\in {\\large{\\bf {R}}}$, located in sites, $x$ of a $d\\geq 2$ dimensional lattice ${\\large{\\bf Z^{d}}}$. \\\\ The spins interacting via nearest neighbors ferromagnetic interactions are embedded in a single spin potential $V$ similar to that, already, introduced by Dobrushin and Shlosman.\\\\ The potential $V$, has an ordered sequence $\\left( \\omega_{1}m_{q^{^{\\prime }}}$, $q< q^{^{\\prime }}$. \\item The distance between two successive minima is sufficiently great and the they are separated by a sufficiently heigh energy barrier. \\end{itemize} For all finite reciprocal temperature $\\beta$, satisfying $1\\leq \\beta <\\infty$, and for the mass $m_{n}$ ( corresponding to the $n^{th}$ minimum) large enough, we prove the Peierls condition, and we derive the phase diagram by proving that there exist sequences ($\\beta_{1},... ,\\beta_{N(n)}$) , $N(n)

  7. Octupole shapes and shape changes at high spins in the Z approx 58, N approx 88 nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Nazarewicz, W. (Department of Physics, Florida State University, Tallahassee, Florida 32306 (United States) Joint Institute for Heavy Ion Research, Holifield Heavy Ion Research Facility, P.O. Box 2008, Oak Ridge, Tennessee 37831 (United States)); Tabor, S.L. (Department of Physics, Florida State University, Tallahassee, Florida 32306 (United States))

    1992-05-01

    The shapes of rotating Xe, Ba, Ce, Nd, and Sm nuclei (84{le}{ital N}{le}94) are calculated using the cranking model with the Woods-Saxon average potential and pairing. The lightest isotopes of Xe and Ba have nearly spherical ground states, but develop octupole and quadrupole deformations under rotation which remain up to very high spins. The ground states of the heavier isotopes have octupole and quadrupole deformations which persist up to medium spins ({ital I}{approx}12{h bar}). At higher spins, a shape transition is predicted to reflection-symmetric aligned many-quasiparticle configurations.

  8. Incremental change, transition or transformation? optimising change pathways for climate adaptation in spatial planning

    National Research Council Canada - National Science Library

    Roggema, R.E; Vermeend, T; Van den Dobbelsteen, A.A.J.F

    2012-01-01

    .... Incremental change is seen as a slow process, which modifies the landscape only slightly. Transition is seen as a fluent change towards a new future, which is an improved version of the existing...

  9. Hot spin spots in the laser-induced demagnetization

    Directory of Open Access Journals (Sweden)

    M. S. Si

    2012-03-01

    Full Text Available Laser-induced femtosecond magnetism or femtomagnetism simultaneously relies on two distinctive contributions: (a the optical dipole interaction (ODI between a laser field and a magnetic system and (b the spin expectation value change (SEC between two transition states. Surprisingly, up to now, no study has taken both contributions into account simultaneously. Here we do so by introducing a new concept of the optical spin generator, a product of SEC and ODI between transition states. In ferromagnetic nickel, our first-principles calculation demonstrates that the larger the value of optical spin generator is, the larger the dynamic spin moment change is. This simple generator directly links the time-dependent spin moment change ΔMzk(t at every crystal-momentum k point to its intrinsic electronic structure and magnetic properties. Those hot spin spots are a direct manifestation of the optical spin generator, and should be the focus of future research.

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

    OpenAIRE

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

    2013-01-01

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

  11. Transgender transitioning and change of self-reported sexual orientation.

    Science.gov (United States)

    Auer, Matthias K; Fuss, Johannes; Höhne, Nina; Stalla, Günter K; Sievers, Caroline

    2014-01-01

    Sexual orientation is usually considered to be determined in early life and stable in the course of adulthood. In contrast, some transgender individuals report a change in sexual orientation. A common reason for this phenomenon is not known. We included 115 transsexual persons (70 male-to-female "MtF" and 45 female-to-male "FtM") patients from our endocrine outpatient clinic, who completed a questionnaire, retrospectively evaluating the history of their gender transition phase. The questionnaire focused on sexual orientation and recalled time points of changes in sexual orientation in the context of transition. Participants were further asked to provide a personal concept for a potential change in sexual orientation. In total, 32.9% (n = 23) MtF reported a change in sexual orientation in contrast to 22.2% (n = 10) FtM transsexual persons (p = 0.132). Out of these patients, 39.1% (MtF) and 60% (FtM) reported a change in sexual orientation before having undergone any sex reassignment surgery. FtM that had initially been sexually oriented towards males ( = androphilic), were significantly more likely to report on a change in sexual orientation than gynephilic, analloerotic or bisexual FtM (p = 0.012). Similarly, gynephilic MtF reported a change in sexual orientation more frequently than androphilic, analloerotic or bisexual MtF transsexual persons (p =0.05). In line with earlier reports, we reveal that a change in self-reported sexual orientation is frequent and does not solely occur in the context of particular transition events. Transsexual persons that are attracted by individuals of the opposite biological sex are more likely to change sexual orientation. Qualitative reports suggest that the individual's biography, autogynephilic and autoandrophilic sexual arousal, confusion before and after transitioning, social and self-acceptance, as well as concept of sexual orientation itself may explain this phenomenon.

  12. Quantum transitions, magnetization and thermal entanglement of the spin-1 Ising-Heisenberg diamond chain

    Science.gov (United States)

    Abgaryan, V. S.; Ananikian, N. S.; Ananikyan, L. N.; Hovhannisyan, V. V.

    2015-12-01

    We consider the quasi-one dimensional spin-1 Ising-Heisenberg model with single-ion anisotropy on a diamond chain. Due to the exact solution of the model, we constructed the ground state phases which, alongside to others, have shown capability to exhibit most interesting frustrated state. The investigation of the magnetization processes showed enrichment of possibilities to form plateaus at zero, one- and two-thirds of the saturation magnetization. Negativity as a measure of the quantum entanglement is considered at low temperatures.

  13. Time-, spin- and energyresolved photoemission microscopy of 3d transition metals

    Energy Technology Data Exchange (ETDEWEB)

    Heitkamp, Bernd; Duerr, H.A.; Eberhardt, W.

    2007-07-01

    Understanding ultrafast de- and remagnetization processes are of considerable interest, since it allows to shorten the read/write-cycles in magnetism based memories. Our approach is to combine the nm-spatial resolution of a photoelectron emission microscopy (PEEM) with a fs time-resolution using the pump-probe technique. Magnetic sensitivity is obtained by detecting the spin of the emitted photoelectrons. Experiments on nickel and cobalt show a demagnetization below one picosecond. Electron- and spindynamics strongly depend on the dielectric response of the nanostructures.

  14. Various quantum measures and quantum phase transition within one-dimensional anisotropic spin-1/2 Heisenberg XXZ model

    Science.gov (United States)

    Sun, Wen-Yang; Wang, Dong; Ye, Liu

    2017-11-01

    In this work, we investigate the dynamical properties of various quantum measures (quantum coherence and correlations) to estimate the system evolution under spin-1/2 Heisenberg XXZ model by utilizing quantum renormalization-group method. It has been shown that quantum coherence and correlations can be used to effectively detect a quantum critical point associated with a quantum phase transition (QPT) after several iterations of renormalization. Additionally, we obtain that the dynamical behavior of l1 norm of coherence is in agreement with that of concurrence and double trace distance discord. Interestingly, Bell-CHSH inequality cannot be violated with increasing of the spin system size N. That is, the block-block Bell nonlocality cannot be revealed. Moreover, we reveal some quantitative relations between quantum coherence and some quantum correlations, and thus the l1 norm of coherence is more conducive for probing the QPT at the critical point within the composite systems. Further, the scaling behaviors and nonanalytic phenomenon of the l1 norm of coherence and quantum discord are discussed in detail.

  15. Field-induced transition from chiral spin-triplet to mixed-parity Fulde-Ferrell-Larkin-Ovchinnikov superconductivity

    Science.gov (United States)

    Romano, Alfonso; Cuoco, Mario; Noce, Canio; Gentile, Paola; Annunziata, Gaetano

    2010-02-01

    We analyze the response to a magnetic field of a two-dimensional spin-triplet superconductor with chiral order parameter when triplet pairing is closely competing with the singlet one. The study is performed via numerical solution of the Bogoliubov-de Gennes equations, assuming that the translational symmetry is broken in one direction by the presence of an interface beyond which superconducting pairing is not effective. We show that as the intensity of the magnetic field is increased above a threshold value, the system undergoes a transition to a spatially inhomogeneous state of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) type where chirality disappears and a singlet-triplet mixing takes place along the direction perpendicular to the interface. Subdominant singlet components are found to accompany the triplet dominant ones in both phases. They develop close to the interface at low fields, then turning continuously into oscillating long-range ones as the field is increased. A similar behavior is found for the magnetization. It nucleates at the interface in the chiral phase, then acquiring in the FFLO phase an oscillatory behavior reaching its maximum amplitude at the sites where the dominant triplet component has a node. At these sites, the local spin-resolved density of states exhibits strong resonances, associated with the formation of Andreev bound states, which tend to broaden and decay in intensity as increasingly high magnetic fields are considered.

  16. Communication: Evaluating non-empirical double hybrid functionals for spin-state energetics in transition-metal complexes

    Science.gov (United States)

    Wilbraham, Liam; Adamo, Carlo; Ciofini, Ilaria

    2018-01-01

    The computationally assisted, accelerated design of inorganic functional materials often relies on the ability of a given electronic structure method to return the correct electronic ground state of the material in question. Outlining difficulties with current density functionals and wave function-based approaches, we highlight why double hybrid density functionals represent promising candidates for this purpose. In turn, we show that PBE0-DH (and PBE-QIDH) offers a significant improvement over its hybrid parent functional PBE0 [as well as B3LYP* and coupled cluster singles and doubles with perturbative triples (CCSD(T))] when computing spin-state splitting energies, using high-level diffusion Monte Carlo calculations as a reference. We refer to the opposing influence of Hartree-Fock (HF) exchange and MP2, which permits higher levels of HF exchange and a concomitant reduction in electronic density error, as the reason for the improved performance of double-hybrid functionals relative to hybrid functionals. Additionally, using 16 transition metal (Fe and Co) complexes, we show that low-spin states are stabilised by increasing contributions from MP2 within the double hybrid formulation. Furthermore, this stabilisation effect is more prominent for high field strength ligands than low field strength ligands.

  17. Rapid Communication: v= 2 seniority changing transitions in yrast 3 ...

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 89; Issue 5. Rapid Communication: Δ υ = 2 seniority changing transitions in yrast 3 − states and B ( E 3 ) systematics of Sn isotopes. BHOOMIKA MAHESHWARI SWATI GARG ASHOK KUMAR JAIN. Research Article Volume 89 Issue 5 November 2017 Article ID 75 ...

  18. Rapid Communication: seniority changing transitions in yrast states ...

    Indian Academy of Sciences (India)

    Bhoomika Maheshwari

    2017-10-26

    Oct 26, 2017 ... Rapid Communication: v = 2 seniority changing transitions in yrast 3− states and B(E3) systematics of Sn isotopes. BHOOMIKA MAHESHWARI1,∗. , SWATI GARG2 and ASHOK KUMAR JAIN2. 1Department of Physics, Banasthali University, Banasthali 304 022, India. 2Department of Physics, IIT Roorkee, ...

  19. Electronic, spin-state, and magnetic transitions in B a2C o9O14 investigated by x-ray spectroscopies and neutron diffraction

    Science.gov (United States)

    Herrero-Martín, J.; Padilla-Pantoja, J.; Lafuerza, S.; Romaguera, A.; Fauth, F.; Reparaz, J. S.; García-Muñoz, J. L.

    2017-06-01

    The mixed B a2C o9O14C o2 +/C o3 + system undergoes an insulator-insulator transition at TSS˜567 K that arises from a spin-state transition at trivalent cobalt sites. Below this temperature, Co1, Co2, and Co4 are nonmagnetic (S =0 , low spin). Ferromagnetically aligned Co5 spins are sandwiched between antiparallel planes of Co3 spins below TN≈41 K . The successive antiferromagnetic trilayers are inverted along the c axis (compatible with Cc2 /c ,Cc2 /m , or PS-1 magnetic space groups, depending on the moment orientation in the a b plane). The origin of the resistivity drop on warming was investigated by means of neutron and x-ray diffraction, x-ray absorption and emission spectroscopies, and x-ray magnetic circular dichroism. Charge-transfer multiplet calculations confirm that the divalent Co sites are both in an S =3 /2 high spin state. Independently, the analysis of measured Co Kβ x-ray emission spectroscopy spectra agrees with this model. The magnetic moment from divalent Co5 ions is not fully ordered, likely due to the competition between magnetic anisotropy and weak supersuperexchange interactions, but not to covalency effects. Results agree with the spin blockade of electronic transport being partially removed at the octahedral trimers and also at the Co 4 O6 units within the Cd I2 -type layer.

  20. EXAFS and X-ray diffraction study of LaCoO3 across the spin-state transition

    Science.gov (United States)

    Sikolenko, V. V.; Troyanchuk, I. O.; Efimov, V. V.; Efimova, E. A.; Tiutiunnikov, S. I.; Karpinsky, D. V.; Pascarelli, S.; Zaharko, O.; Ignatov, A.; Aquilanti, D.; Selutin, A. G.; Shmakov, A. N.; Prabhakaran, D.

    2016-05-01

    A combined high-resolution Co K-edge extended x-ray absorption fine structure (EXAFS) and high-resolution X-ray powder diffraction (XRD) study has been performed to clarify the detail of anomalous behavior of temperature-dependent magnetic susceptibility curve on the LaCoO3 across the spin-state (∼120 K) transition. According to XRD analysis, the Debye-Waller factor of Co-O bond exhibit rapid growth below 20 K whereas the temperature dependence of the average Co-O bond length shows linear behavior from 10 K to 400 K. The EXAFS data show an anomalous decrease of the Co-O bond lengths with respect to those obtained by XRD. No local distortion of CoO6 octahedral as temperature increases up to 400 K has been detected.

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

    Directory of Open Access Journals (Sweden)

    S. Fujieda

    2016-05-01

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

  2. Dielectric response to the low-temperature magnetic defect structure and spin state transition in polycrystalline LaCoO3

    Science.gov (United States)

    Schmidt, Rainer; Wu, J.; Leighton, C.; Terry, I.

    2009-03-01

    The dielectric and magnetic properties and their correlations were investigated in polycrystalline perovskite LaCoO3-δ . The intrinsic bulk and grain-boundary (GB) dielectric relaxation processes were deconvoluted using impedance spectroscopy between 20 and 120 K, and resistivity and capacitance were analyzed separately. A thermally induced magnetic transition from a Co3+ low-spin (LS) (S=0;t2g6eg0) to a higher spin state occurs at Ts1≈80K , which is controversial in nature and has been suggested to be an intermediate-spin (IS) state (S=1;t2g5eg1) or a high-spin (HS) state (S=2;t2g4eg2) transition. This spin state transition was confirmed by magnetic-susceptibility measurements and was reflected in the impedance by a split of the single GB relaxation process into two coexisting contributions. This apparent electronic phase coexistence at T>80K was interpreted as a reflection of the coexistence of magnetic LS and IS/HS states. At lower temperatures (T≤40K) perceptible variation in bulk dielectric permittivity with temperature appeared to be correlated with the magnetic susceptibility associated with a magnetic defect structure. At 40Kdefect-related magnetism.

  3. Mechanisms of spin-flipping and metal-insulator transition in nano-Fe3O4

    Science.gov (United States)

    Dito Fauzi, Angga; Aziz Majidi, Muhammad; Rusydi, Andrivo

    2017-04-01

    Fe3O4 is a half-metallic ferrimagnet with {{T}\\text{C}}˜ 860 K exhibiting metal-insulator transition (MIT) at  ˜120 K. In bulk form, the saturation magnetization is 0.6 Tesla (˜471 emu cm-3). A recent experimental study has shown that the saturation magnetization of nano-Fe3O4 thin films can achieve up to  ˜760 emu cm-3, attributed to spin-flipping of Fe ions at tetrahedral sites assisted by oxygen vacancies (V O). Such a system has shown to have higher MIT temperature (˜150 K). The spin-flipping is a new phenomenon in Fe3O4, while the MIT is a long-standing one. Here, we propose a model and calculations to investigate the mechanisms of both phenomena. Our results show that, for the system without V O, the ferrimagnetic configuration is energetically favorable. Remakably, upon inclusion of V O, the ground-state configuration switches into ferromagnetic. As for the MIT, by proposing temperature dependences of some hopping integrals in the model, we demonstrate that the system without and with V O undergo the MIT in slightly different ways, leading to higher MIT temperature for the system with V O, in agreement with the experimental data. Our results also show that the MIT in both systems occur concomitantly with the redistribution of electrons among the three Fe ions in each Fe3O4 formula unit. As such temperature dependences of hopping integrals may arise due to dynamic Jahn-Teller effects, our phenomenological theory may provide a way to reconcile existing theories relating the MIT to the structural transition and the charge ordering.

  4. An EPR spin probe method for characterizing changes in the accessible regions of coal upon oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Sady, W.; Kispert, L.D.; Spears, D.R.

    1992-09-01

    Eight Argonne Premium Coal Samples (APCS) were weathered in air and the structural and chemical changes that upon swelling with toluene and pyridine were, examined by an EPR spin probe method developed in this laboratory. Under mild oxidation conditions and swelling with toluene large structural changes were observed for lignite (Beulah-Zap) which suggested the collapse of the coal structure. This did not occur for higher rank coal. Upon oxidation and swelling with toluene and pyridine an increase occurred in the amino substituted spin probe concentration for coals with the carbon percent above 80%. A maximum was found for the creation of 5 {Angstrom} diameter pores upon swelling with pyridine at 85% C.

  5. An EPR spin probe method for characterizing changes in the accessible regions of coal upon oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Sady, W.; Kispert, L.D.; Spears, D.R.

    1992-01-01

    Eight Argonne Premium Coal Samples (APCS) were weathered in air and the structural and chemical changes that upon swelling with toluene and pyridine were, examined by an EPR spin probe method developed in this laboratory. Under mild oxidation conditions and swelling with toluene large structural changes were observed for lignite (Beulah-Zap) which suggested the collapse of the coal structure. This did not occur for higher rank coal. Upon oxidation and swelling with toluene and pyridine an increase occurred in the amino substituted spin probe concentration for coals with the carbon percent above 80%. A maximum was found for the creation of 5 {Angstrom} diameter pores upon swelling with pyridine at 85% C.

  6. Spin dynamics and structural phase transitions in quasi-2D R sub 2 CuO sub 4 (R=Pr, Sm and Eu) antiferromagnetics

    CERN Document Server

    Golovenchits, E I

    2001-01-01

    One studied spin dynamics and dynamics of lattice in R sub 2 CuO sub 4 (R = Pr, Sm, and Eu) crystals within 20-250 GHz frequency range and within 50350 K temperature interval. One detected abrupt variation of absorption coefficient within wide range of frequencies above 120 GHz at 20, 80 and 150 K temperatures in R sub 2 CuO sub 4 (R = Pr, Sm, and Eu), respectively. Absorption jumpings result from structural phase transitions. Wide ranges of spin-wave excitations were observed in all examined crystals in high-temperature phase. Close to temperatures of phase transitions within wide range of frequencies including frequencies corresponding to ranges of spin-wave excitations one observed lines of a absorption caused by lattice dynamics

  7. Phase Transitions in One-Dimensional Truncated Bosonic Hubbard Model and Its Spin-1 Analog

    OpenAIRE

    Kashurnikov, V. A.; Krasavin, A.V.; Svistunov, B. V.

    1997-01-01

    We study one-dimensional truncated (no more than 2 particles on a site) bosonic Hubbard model in both repulsive and attractive regimes by exact diagonalization and exact worldline Monte Carlo simulation. In the commensurate case (one particle per site) we demonstrate that the point of Mott-insulator -- superfluid transition, $(U/t)_c=0.50\\pm 0.05$, is remarkably far from that of the full model. In the attractive region we observe the phase transition from one-particle superfluid to two-partic...

  8. Effect of cluster structure on the transition from spin-dependent tunneling to percolation mechanism of conductivity in LaSr(Ca)MnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Okunev, V.D. [Donetsk Physiko-Technical Institute, Ukrainian National Academy of Sciences, R. Luxemburg str. 72, 83114 Donetsk (Ukraine)]. E-mail: okunev@mail.fti.ac.donetsk.ua; Samoilenko, Z.A. [Donetsk Physiko-Technical Institute, Ukrainian National Academy of Sciences, R. Luxemburg str. 72, 83114 Donetsk (Ukraine); Pafomov, N.N. [Donetsk Physiko-Technical Institute, Ukrainian National Academy of Sciences, R. Luxemburg str. 72, 83114 Donetsk (Ukraine); Plehov, A.L. [Donetsk Physiko-Technical Institute, Ukrainian National Academy of Sciences, R. Luxemburg str. 72, 83114 Donetsk (Ukraine); Szymczak, R. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Baran, M. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Szymczak, H. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Lewandowski, S.J. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Gierlowski, P. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Abal' oshev, A. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland)

    2004-11-15

    We found that the transition from spin-dependent tunneling to percolation mechanism of conductivity in monocrystalline LaCa(Sr)MnO films containing metallic clusters is accompanied by a sharp increase in the efficiency of interaction between atomic, magnetic and electronic subsystems, and the maximum of magnetoresistance is shifted from low to high temperatures.

  9. Influence of pairing on the ({ital p},{ital t}) transition strength between high-spin {ital K} isomers of Hf isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Kuzmenko, N.K. [V. G. Khlopin Radium Institute, 2nd Murinsky Prosp. 28, St. Petersburg 194021 (Russian Federation); Mikhajlov, V.M. [Institute of Physics, St. Petersburg State University, St. Petersburg 19804 (Russian Federation)

    1995-05-01

    The influence of pairing on the probability of the two-nucleon-transfer transition between high-spin {ital K} isomers of Hf isotopes is discussed. Calculations of energies and cross sections are performed by using the particle number projection (FBCS method). In contrast with BCS, the FBCS method predicts that the pairing in many-quasiparticles states does not disappear.

  10. Paleoclimatic change, disaster history and the urbanscape transitions in Athens

    Science.gov (United States)

    Yang, Liang

    2017-04-01

    Past abrupt climate changes on millennium time scales have received wide attention among natural and social scientists, also because of today's rapid climate changes and their extensive impacts on our society. In the eastern Mediterranean area, coherent patterns and synchronous events in history suggest obvious links between urban development and climate forcing. The city of Athens as the origin of ancient Greek civilization experienced many periods of prosperity and decay. Though the transitions were mostly dominated by wars and power changes between empires, severe climate events and natural disasters may also considerably have shaped the process of Athens' development. Among natural disasters, earthquake, tsunami, flood and wildfire were the main forces that stressed the development of Athens. To recover from and respond to these disaster impacts, the city was thereafter developed in ways that either changed the ever existed city patterns or guided sensitive areas to specific directions, which could have transformed the urbanscape gradually. However, the possibility that these transitions may have been responses/resilience strategies triggered by abrupt climate events has so far hardly been explored. With extensive literature review, existing archaeological records and paleoclimate reconstruction modelling results, this study analyzes the large scale climate variations, related environment changes in mesoscale, aiming at setting into context the local natural disasters in Athens and its surrounding areas during the Holocene period. The study treats a number of important climate events in the area and urban transitions of the city, of which the integration of all these elements and insights from recent analysis throw some new light on understanding the forcing-transition process. Preliminary results indicate unclear link of climate forcing and urban transition over the whole city, but a few signs of possible linkages were recognized at specific blocks of Athens

  11. Quantum critical local spin dynamics near the Mott metal-insulator transition in infinite dimensions

    Science.gov (United States)

    Dasari, Nagamalleswararao; Vidhyadhiraja, N. S.; Jarrell, Mark; McKenzie, Ross H.

    2017-04-01

    Finding microscopic models for metallic states that exhibit quantum critical properties is a major theoretical challenge. We calculate the dynamical local spin susceptibility χ (T ,ω ) for a Hubbard model at half-filling using dynamical mean-field theory, which is exact in infinite dimensions. Qualitatively distinct behavior is found in the different regions of the phase diagram: Mott insulator, Fermi liquid metal, bad metal, and a quantum critical region above the finite-temperature critical point. The signature of the latter is ω /T scaling, where ω is the frequency and T is the temperature. Our results are consistent with previous results showing scaling of the dc electrical conductivity, and they are relevant to experiments on organic charge-transfer salts.

  12. Spin-crossover materials properties and applications

    CERN Document Server

    Halcrow, Malcolm A

    2013-01-01

    The phenomenon of spin-crossover has a large impact on the physical properties of a solid material, including its colour, magnetic moment, and electrical resistance. Some materials also show a structural phase change during the transition. Several practical applications of spin-crossover materials have been demonstrated including display and memory devices, electrical and electroluminescent devices, and MRI contrast agents. Switchable liquid crystals, nanoparticles, and thin films of spin-crossover materials have also been achieved. Spin-Crossover Materials: Properties and Applicat

  13. Renormalization group and phase transitions in spin, gauge, and QCD like theories

    Science.gov (United States)

    Liu, Yuzhi

    In this thesis, we study several different renormalization group (RG) methods, including the conventional Wilson renormalization group, Monte Carlo renormalization group (MCRG), exact renormalization group (ERG, or sometimes called functional RG), and tensor renormalization group (TRG). We use the two dimensional nearest neighbor Ising model to introduce many conventional yet important concepts. We then generalize the model to Dyson's hierarchical model (HM), which has rich phase properties depending on the strength of the interaction. The partition function zeros (Fisher zeros) of the HM model in the complex temperature plane is calculated and their connection with the complex RG flows is discussed. The two lattice matching method is used to construct both the complex RG flows and calculate the discrete beta functions. The motivation of calculating the discrete beta functions for various HM models is to test the matching method and to show how physically relevant fixed points emerge from the complex domain. We notice that the critical exponents calculated from the HM depend on the blocking parameter b. This motivated us to analyze the connection between the discrete and continuous RG transformation. We demonstrate numerical calculations of the ERG equations. We discuss the relation between Litim and Wilson-Polchinski equation and the effect of the cut-off functions in the ERG calculation. We then apply methods developed in the spin models to more complicated and more physically relevant lattice gauge theories and lattice quantum chromodynamics (QCD) like theories. Finite size scaling (FSS) technique is used to analyze the Binder cumulant of the SU(2) lattice gauge model. We calculate the critical exponent nu and omega of the model and show that it is in the same universality class as the three dimensional Ising model. Motivated by the walking technicolor theory, we study the strongly coupled gauge theories with conformal or near conformal properties. We compare

  14. Finite-temperature phase transition to a Kitaev spin liquid phase on a hyperoctagon lattice: A large-scale quantum Monte Carlo study

    Science.gov (United States)

    Mishchenko, Petr A.; Kato, Yasuyuki; Motome, Yukitoshi

    2017-09-01

    The quantum spin liquid is an enigmatic quantum state in insulating magnets, in which conventional long-range order is suppressed by strong quantum fluctuations. Recently, an unconventional phase transition was reported between the low-temperature quantum spin liquid and the high-temperature paramagnet in the Kitaev model on a three-dimensional hyperhoneycomb lattice. Here, we show that a similar "liquid-gas" transition takes place in another three-dimensional lattice, the hyperoctagon lattice. We investigate the critical phenomena by adopting the Green-function based Monte Carlo technique with the kernel polynomial method, which enables systematic analysis of up to 2048 sites. The critical temperature is lower than that in the hyperhoneycomb case, reflecting the smaller flux gap. We also discuss the transition on the basis of an effective model in the anisotropic limit.

  15. Complex Nonlinearity Chaos, Phase Transitions, Topology Change and Path Integrals

    CERN Document Server

    Ivancevic, Vladimir G

    2008-01-01

    Complex Nonlinearity: Chaos, Phase Transitions, Topology Change and Path Integrals is a book about prediction & control of general nonlinear and chaotic dynamics of high-dimensional complex systems of various physical and non-physical nature and their underpinning geometro-topological change. The book starts with a textbook-like expose on nonlinear dynamics, attractors and chaos, both temporal and spatio-temporal, including modern techniques of chaos–control. Chapter 2 turns to the edge of chaos, in the form of phase transitions (equilibrium and non-equilibrium, oscillatory, fractal and noise-induced), as well as the related field of synergetics. While the natural stage for linear dynamics comprises of flat, Euclidean geometry (with the corresponding calculation tools from linear algebra and analysis), the natural stage for nonlinear dynamics is curved, Riemannian geometry (with the corresponding tools from nonlinear, tensor algebra and analysis). The extreme nonlinearity – chaos – corresponds to th...

  16. Geometric structure and information change in phase transitions.

    Science.gov (United States)

    Kim, Eun-Jin; Hollerbach, Rainer

    2017-06-01

    We propose a toy model for a cyclic order-disorder transition and introduce a geometric methodology to understand stochastic processes involved in transitions. Specifically, our model consists of a pair of forward and backward processes (FPs and BPs) for the emergence and disappearance of a structure in a stochastic environment. We calculate time-dependent probability density functions (PDFs) and the information length L, which is the total number of different states that a system undergoes during the transition. Time-dependent PDFs during transient relaxation exhibit strikingly different behavior in FPs and BPs. In particular, FPs driven by instability undergo the broadening of the PDF with a large increase in fluctuations before the transition to the ordered state accompanied by narrowing the PDF width. During this stage, we identify an interesting geodesic solution accompanied by the self-regulation between the growth and nonlinear damping where the time scale τ of information change is constant in time, independent of the strength of the stochastic noise. In comparison, BPs are mainly driven by the macroscopic motion due to the movement of the PDF peak. The total information length L between initial and final states is much larger in BPs than in FPs, increasing linearly with the deviation γ of a control parameter from the critical state in BPs while increasing logarithmically with γ in FPs. L scales as |lnD| and D^{-1/2} in FPs and BPs, respectively, where D measures the strength of the stochastic forcing. These differing scalings with γ and D suggest a great utility of L in capturing different underlying processes, specifically, diffusion vs advection in phase transition by geometry. We discuss physical origins of these scalings and comment on implications of our results for bistable systems undergoing repeated order-disorder transitions (e.g., fitness).

  17. Geometric structure and information change in phase transitions

    Science.gov (United States)

    Kim, Eun-jin; Hollerbach, Rainer

    2017-06-01

    We propose a toy model for a cyclic order-disorder transition and introduce a geometric methodology to understand stochastic processes involved in transitions. Specifically, our model consists of a pair of forward and backward processes (FPs and BPs) for the emergence and disappearance of a structure in a stochastic environment. We calculate time-dependent probability density functions (PDFs) and the information length L , which is the total number of different states that a system undergoes during the transition. Time-dependent PDFs during transient relaxation exhibit strikingly different behavior in FPs and BPs. In particular, FPs driven by instability undergo the broadening of the PDF with a large increase in fluctuations before the transition to the ordered state accompanied by narrowing the PDF width. During this stage, we identify an interesting geodesic solution accompanied by the self-regulation between the growth and nonlinear damping where the time scale τ of information change is constant in time, independent of the strength of the stochastic noise. In comparison, BPs are mainly driven by the macroscopic motion due to the movement of the PDF peak. The total information length L between initial and final states is much larger in BPs than in FPs, increasing linearly with the deviation γ of a control parameter from the critical state in BPs while increasing logarithmically with γ in FPs. L scales as |lnD | and D-1 /2 in FPs and BPs, respectively, where D measures the strength of the stochastic forcing. These differing scalings with γ and D suggest a great utility of L in capturing different underlying processes, specifically, diffusion vs advection in phase transition by geometry. We discuss physical origins of these scalings and comment on implications of our results for bistable systems undergoing repeated order-disorder transitions (e.g., fitness).

  18. Magnetic phase transitions in ferrite nanoparticles characterized by electron spin resonance

    Energy Technology Data Exchange (ETDEWEB)

    Flores-Arias, Yesica, E-mail: yeika01@hotmail.com; Vázquez-Victorio, Gabriela; Ortega-Zempoalteca, Raul; Acevedo-Salas, Ulises; Valenzuela, Raul [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, México D.F. 04510 (Mexico); Ammar, Souad [Laboratoires ITODYS, Université de Paris-Diderot, PRES Sorbonne Paris Cité, CNRS-UMR 7086, 75205 Paris Cedex (France)

    2015-05-07

    Ferrite magnetic nanoparticles in the composition Zn{sub 0.7}Ni{sub 0.3}Fe{sub 2}O{sub 4} were synthesized by the polyol method, with an average size of 8 nm. Electron spin resonance (ESR) measurements were carried out at a frequency of 9.45 GHz in the 100–500 K temperature range. Obtained results exhibited a characteristic ESR signal in terms of resonance field, H{sub res}, linewidth, ΔH, and peak ratio, R, for each magnetic phase. At low temperatures, the ferrimagnetic phase showed low H{sub res}, broad ΔH, and asymmetric R. At high temperatures, these parameters exhibited opposite values: high H{sub res}, small ΔH, and R ∼ 1. For intermediate temperatures, a different phase was observed, which was identified as a superparamagnetic phase by means of zero-field cooling-field cooling and hysteresis loops measurements. The observed differences were explained in terms of the internal fields and especially due to the cubic anisotropy in the ordered phase.

  19. Transgender transitioning and change of self-reported sexual orientation.

    Directory of Open Access Journals (Sweden)

    Matthias K Auer

    Full Text Available Sexual orientation is usually considered to be determined in early life and stable in the course of adulthood. In contrast, some transgender individuals report a change in sexual orientation. A common reason for this phenomenon is not known.We included 115 transsexual persons (70 male-to-female "MtF" and 45 female-to-male "FtM" patients from our endocrine outpatient clinic, who completed a questionnaire, retrospectively evaluating the history of their gender transition phase. The questionnaire focused on sexual orientation and recalled time points of changes in sexual orientation in the context of transition. Participants were further asked to provide a personal concept for a potential change in sexual orientation.In total, 32.9% (n = 23 MtF reported a change in sexual orientation in contrast to 22.2% (n = 10 FtM transsexual persons (p = 0.132. Out of these patients, 39.1% (MtF and 60% (FtM reported a change in sexual orientation before having undergone any sex reassignment surgery. FtM that had initially been sexually oriented towards males ( = androphilic, were significantly more likely to report on a change in sexual orientation than gynephilic, analloerotic or bisexual FtM (p = 0.012. Similarly, gynephilic MtF reported a change in sexual orientation more frequently than androphilic, analloerotic or bisexual MtF transsexual persons (p =0.05.In line with earlier reports, we reveal that a change in self-reported sexual orientation is frequent and does not solely occur in the context of particular transition events. Transsexual persons that are attracted by individuals of the opposite biological sex are more likely to change sexual orientation. Qualitative reports suggest that the individual's biography, autogynephilic and autoandrophilic sexual arousal, confusion before and after transitioning, social and self-acceptance, as well as concept of sexual orientation itself may explain this phenomenon.

  20. Transgender Transitioning and Change of Self-Reported Sexual Orientation

    Science.gov (United States)

    Höhne, Nina; Stalla, Günter K.; Sievers, Caroline

    2014-01-01

    Objective Sexual orientation is usually considered to be determined in early life and stable in the course of adulthood. In contrast, some transgender individuals report a change in sexual orientation. A common reason for this phenomenon is not known. Methods We included 115 transsexual persons (70 male-to-female “MtF” and 45 female-to-male “FtM”) patients from our endocrine outpatient clinic, who completed a questionnaire, retrospectively evaluating the history of their gender transition phase. The questionnaire focused on sexual orientation and recalled time points of changes in sexual orientation in the context of transition. Participants were further asked to provide a personal concept for a potential change in sexual orientation. Results In total, 32.9% (n =  23) MtF reported a change in sexual orientation in contrast to 22.2% (n =  10) FtM transsexual persons (p =  0.132). Out of these patients, 39.1% (MtF) and 60% (FtM) reported a change in sexual orientation before having undergone any sex reassignment surgery. FtM that had initially been sexually oriented towards males ( = androphilic), were significantly more likely to report on a change in sexual orientation than gynephilic, analloerotic or bisexual FtM (p  =  0.012). Similarly, gynephilic MtF reported a change in sexual orientation more frequently than androphilic, analloerotic or bisexual MtF transsexual persons (p  =  0.05). Conclusion In line with earlier reports, we reveal that a change in self-reported sexual orientation is frequent and does not solely occur in the context of particular transition events. Transsexual persons that are attracted by individuals of the opposite biological sex are more likely to change sexual orientation. Qualitative reports suggest that the individual's biography, autogynephilic and autoandrophilic sexual arousal, confusion before and after transitioning, social and self-acceptance, as well as concept of sexual orientation itself may

  1. Spin Resonance Clock Transition of the Endohedral Fullerene 15N @ C60

    Science.gov (United States)

    Harding, R. T.; Zhou, S.; Zhou, J.; Lindvall, T.; Myers, W. K.; Ardavan, A.; Briggs, G. A. D.; Porfyrakis, K.; Laird, E. A.

    2017-10-01

    The endohedral fullerene 15N @ C60 has narrow electron paramagnetic resonance lines which have been proposed as the basis for a condensed-matter portable atomic clock. We measure the low-frequency spectrum of this molecule, identifying and characterizing a clock transition at which the frequency becomes insensitive to magnetic field. We infer a linewidth at the clock field of 100 kHz. Using experimental data, we are able to place a bound on the clock's projected frequency stability. We discuss ways to improve the frequency stability to be competitive with existing miniature clocks.

  2. A combined DFT and restricted open-shell configuration interaction method including spin-orbit coupling: application to transition metal L-edge X-ray absorption spectroscopy.

    Science.gov (United States)

    Roemelt, Michael; Maganas, Dimitrios; DeBeer, Serena; Neese, Frank

    2013-05-28

    A novel restricted-open-shell configuration interaction with singles (ROCIS) approach for the calculation of transition metal L-edge X-ray absorption spectra is introduced. In this method, one first calculates the ground state and a number of excited states of the non-relativistic Hamiltonian. By construction, the total spin is a good quantum number in each of these states. For a ground state with total spin S excited states with spin S' = S, S - 1, and S + 1 are constructed. Using Wigner-Eckart algebra, all magnetic sublevels with MS = S,..., -S for each multiplet of spin S are obtained. The spin-orbit operator is represented by a mean-field approximation to the full Breit-Pauli spin-orbit operator and is diagonalized over this N-particle basis. This is equivalent to a quasi-degenerate treatment of the spin-orbit interaction to all orders. Importantly, the excitation space spans all of the molecular multiplets that arise from the atomic Russell-Saunders terms. Hence, the method represents a rigorous first-principles approach to the complicated low-symmetry molecular multiplet problem met in L-edge X-ray absorption spectroscopy. In order to gain computational efficiency, as well as additional accuracy, the excitation space is restricted to single excitations and the configuration interaction matrix is slightly parameterized in order to account for dynamic correlation effects in an average way. To this end, it is advantageous to employ Kohn-Sham rather than Hartree-Fock orbitals thus defining the density functional theory∕ROCIS method. However, the method can also be used in an entirely non-empirical fashion. Only three global empirical parameters are introduced and have been determined here for future application of the method to any system containing any transition metal. The three parameters were carefully calibrated using the L-edge X-ray absorption spectroscopy spectra of a test set of coordination complexes containing first row transition metals. These

  3. A two-step field-induced magnetic transition in spin-canted systems observed only for the CoII coordination polymer.

    Science.gov (United States)

    Jia, Hong-Peng; Li, Wei; Ju, Zhan-Feng; Zhang, Jie

    2008-01-21

    Two isostructural 1D compounds {[M3(hpdc)2(H2O)6] 2H2O}n (M = Mn, Co; H3hpde = 2-hydroxypyrimidine-4,6-dicarboxylic acid) were synthesized by the in situ hydrothermal reactions of 2-chloropyrimidine-4,6-dicarboxylic acid with MCl2 (M = Mn, Co) and NaOH; the MnII compound shows spin-canted antiferromagnetism, whereas the CoII compound exhibits the coexistence of spin-canting and a two-step field-induced magnetic phase transition.

  4. Electric-Field Modulation of Interface Magnetic Anisotropy and Spin Reorientation Transition in (Co/Pt)3/PMN-PT Heterostructure.

    Science.gov (United States)

    Sun, Ying; Ba, You; Chen, Aitian; He, Wei; Wang, Wenbo; Zheng, Xiaoli; Zou, Lvkuan; Zhang, Yijun; Yang, Qu; Yan, Lingjia; Feng, Ce; Zhang, Qinghua; Cai, Jianwang; Wu, Weida; Liu, Ming; Gu, Lin; Cheng, Zhaohua; Nan, Ce-Wen; Qiu, Ziqiang; Wu, Yizheng; Li, Jia; Zhao, Yonggang

    2017-03-29

    We report electric-field control of magnetism of (Co/Pt) 3 multilayers involving perpendicular magnetic anisotropy with different Co-layer thicknesses grown on Pb(Mg,Nb)O 3 -PbTiO 3 (PMN-PT) FE substrates. For the first time, electric-field control of the interface magnetic anisotropy, which results in the spin reorientation transition, was demonstrated. The electric-field-induced changes of the bulk and interface magnetic anisotropies can be understood by considering the strain-induced change of magnetoelastic energy and weakening of Pt 5d-Co 3d hybridization, respectively. We also demonstrate the role of competition between the applied magnetic field and the electric field in determining the magnetization of the sample with the coexistence phase. Our results demonstrate electric-field control of magnetism by harnessing the strain-mediated coupling in multiferroic heterostructures with perpendicular magnetic anisotropy and are helpful for electric-field modulations of Dzyaloshinskii-Moriya interaction and Rashba effect at interfaces to engineer new functionalities.

  5. Quantitative Glycopeptide Changes in Rat Sperm During Epididymal Transit.

    Science.gov (United States)

    Villaverde, Ana Izabel Silva Balbin; Hetherington, Louise; Baker, Mark A

    2016-04-01

    Mammalian spermatozoa acquire fertilizing potential as they undergo a series of changes during epididymal transit. One major facet of such is the alterations in the sperm glycome. Modifications of the sialic acid content within glycan moieties are known to regulate epitope presentation and cellular adhesion and signaling, all of which may be critical for sperm to successfully reach and fertilize the egg. To date, there is paucity of information regarding the sialic acid changes that occur on spermatozoa during epididymal transit. Therefore, the aim of this study was to identify N-linked sialylated glycoproteins in rat epididymal sperm and investigate whether they are regulated during epididymal transit. Sialylated glycopeptides from caput, corpus, and cauda spermatozoa were enriched using titanium dioxide beads. Bound N-linked glycopeptides were released by enzymatic deglycosylation using PNGase F and then analyzed by liquid chromatography tandem-mass spectrometry. A total of 92 unique N-linked sialylated glycopeptides were identified from 65 different proteins. These included members of the disintegrin and metalloproteinase domain-containing protein family (ADAM), Basigin, and Testis-expressed protein 101 (TEX101). Remarkably, label-free quantification showed that more than half of these peptides (48/92) were regulated during epididymal transit. Of interest, the protein TEX101 exhibited PNGase F-resistant deglycosylation under the conditions used in this study. The results from this study showed that changes in the N-linked sialoglycoprotein profile is a major hallmark of sperm maturation in rats. © 2016 by the Society for the Study of Reproduction, Inc.

  6. Changes in element composition along the spinning duct in a Nephila spider

    Science.gov (United States)

    Knight, David; Vollrath, Fritz

    2001-05-01

    The silk gland of the golden orb spider Nephila edulis connects to the exit spigot through a long S-shaped duct that assists in the formation of the thread. Previous evidence suggests that the epithelium of the distal (last) part of the duct is specialized for ion transport and that a proton pump is involved in this process. Here, we present evidence from SEM (scanning electron microscope)-EDAX (energy dispersive X-ray) microanalysis of rapidly frozen material maintained at approximately -150°C and from the use of pH indicators that the element composition and pH change progressively as the dragline silk dope (spinning solution) passes down the duct to form the thread. Na+ and Cl- composition decreased while K+ and P and S increased. Indicators suggested that the pH dropped from 6.9+/-0.1 to 6.3+/-0.1. These novel findings suggest that the absorption of Na+ and secretion of the more chaotropic K+ may help the silk protein molecules to refold while the secretion of H+ may assist in this process and reduce the repulsive charges on them. This in turn may allow the molecules to approach one another more closely to crystallize. Thus precise control of the ionic environment within the spider's spinning duct may be important in forming a tough insoluble thread and when devising mimetic processes to spin silk proteins industrially.

  7. Nonclassical effects of a two-level spin system interacting with a two-mode cavity field via two-photon transition.

    Science.gov (United States)

    Grinberg, Horacio

    2008-12-18

    The interaction of a two-level cyclic XY n-spin model with a two-mode cavity field involving two-photon transitions is investigated through a generalized Jaynes-Cummings model in the rotating-wave approximation. The two-photon interacting Hamiltonian becomes from the replacement of each single-mode field in the one-photon interacting Hamiltonian with the second-harmonic generation. It was assumed that initially the correlated field modes are in disentangled coherent states having the same photon distribution and that the spin system is in an excited state. At any time t > 0, the spin system and the field are in an entangled state, in this case, via a unitary time evolution operator. Thus, the spontaneous decay of a spin level was treated by considering the interaction of the two-level spin system with the modes of the universe in the vacuum state. The different cases of interest, characterized in terms of a detuning parameter for each mode, which emerge from nonvanishing commutation relations, were analytically implemented and numerically discussed for various values of the initial mean photon number and spin-photon coupling constants. Photon distribution, time evolution of the spin population inversion, as well as the statistical properties of the field leading to the possible production of nonclassical states, such as antibunched light, violations of the Cauchy-Schwartz inequality, and second- and fourth-order squeezing, are examined. The case of zero detuning of both modes was treated in terms of a linearization of the expansion of the time evolution operator, while in other three cases, the computations were conducted via second- and third-order Dyson perturbation expansion of the time evolution operator matrix elements for the excited and ground states of the spin system, respectively.

  8. 3D spin-flop transition in enhanced 2D layered structure single crystalline TlCo2Se2

    Science.gov (United States)

    Jin, Z.; Xia, Z.-C.; Wei, M.; Yang, J.-H.; Chen, B.; Huang, S.; Shang, C.; Wu, H.; Zhang, X.-X.; Huang, J.-W.; Ouyang, Z.-W.

    2016-10-01

    The enhanced 2D layered structure single crystalline TlCo2Se2 has been successfully fabricated, which exhibits field-induced 3D spin-flop phase transitions. In the case of the magnetic field parallel to the c-axis (B//c), the applied magnetic field induces the evolution of the noncollinear helical magnetic coupling into a ferromagnetic (FM) state with all the magnetization of the Co ion parallel to the c-axis. A striking variation of the field-induced strain within the ab-plane is noticed in the magnetic field region of 20-30 T. In the case of the magnetic field perpendicular to the c-axis (B  ⊥  c), the inter-layer helical antiferromagnetic (AFM) coupling may transform to an initial canted AFM coupling, and then part of it transforms to an intermediate metamagnetic phase with the alignment of two-up-one-down Co magnetic moments and finally to an ultimate FM coupling in higher magnetic fields. The robust noncollinear AFM magnetic coupling is completely destroyed above 30 T. In combination with the measurements of magnetization, magnetoresistance and field-induced strain, a complete magnetic phase diagram of the TlCo2Se2 single crystal has been depicted, demonstrating complex magnetic structures even though the crystal geometry itself gives no indication of the magnetic frustration.

  9. The need for a change in the paradigm of entrepreneurship at universities: differences between innovative spin-offs and technology-based spin-offs

    Directory of Open Access Journals (Sweden)

    Enara Zarrabeitia

    2016-05-01

    Full Text Available This study seeks to analyse the main characteristics of and barriers to the growth and development of innovative university spin-offs (which originate mainly from the fields of social science and law and technology-based university spin-offs (which tend to originate from the experimental sciences, from technical studies and from health science. The idea is to examine whether there is a need to redirect university policies aimed in the field of entrepreneurship. The study is based on a sample of 40 university spin-offs originating from the University of the Basque Country (UPV/EHU. A questionnaire was sent to entrepreneurs identified with the aid of the persons in charge of the university programmes for creating businesses at the UPV/EHU. To determine the main differences between innovative and technology-based spin-offs, once the replies were received a bivariate or contingent analysis was applied to characterise the two types of business. The main barriers to growth and development encountered by the two types were then identified. The data analysed reveal significant differences between the two types of business, and a need for a change in the paradigm of university entrepreneurship.

  10. Relativistic quark-diquark model of baryons with a spin-isospin transition interaction: Non-strange baryon spectrum and nucleon magnetic moments

    Energy Technology Data Exchange (ETDEWEB)

    Sanctis, M. de [Universidad Nacional de Colombia, Bogota (Colombia); Ferretti, J. [Universita La Sapienza, Dipartimento di Fisica, Roma (Italy); INFN, Roma (Italy); Santopinto, E.; Vassallo, A. [INFN, Sezione di Genova, Genova (Italy)

    2016-05-15

    The relativistic interacting quark-diquark model of baryons, recently developed, is here extended introducing in the mass operator a spin-isospin transition interaction. This refined version of the model is used to calculate the non-strange baryon spectrum. The results are compared to the present experimental data. A preliminary calculation of the magnetic moments of the proton and neutron is also presented. (orig.)

  11. Quantum spin Hall effect and topological phase transition in InN x Bi y Sb1-x-y /InSb quantum wells

    Science.gov (United States)

    Song, Zhigang; Bose, Sumanta; Fan, Weijun; Zhang, Dao Hua; Zhang, Yan Yang; Shen Li, Shu

    2017-07-01

    Quantum spin Hall (QSH) effect, a fundamentally new quantum state of matter and topological phase transitions are characteristics of a kind of electronic material, popularly referred to as topological insulators (TIs). TIs are similar to ordinary insulator in terms of their bulk bandgap, but have gapless conducting edge-states that are topologically protected. These edge-states are facilitated by the time-reversal symmetry and they are robust against nonmagnetic impurity scattering. Recently, the quest for new materials exhibiting non-trivial topological state of matter has been of great research interest, as TIs find applications in new electronics and spintronics and quantum-computing devices. Here, we propose and demonstrate as a proof-of-concept that QSH effect and topological phase transitions can be realized in {{InN}}x{{Bi}}y{{Sb}}1-x-y/InSb semiconductor quantum wells (QWs). The simultaneous incorporation of nitrogen and bismuth in InSb is instrumental in lowering the bandgap, while inducing opposite kinds of strain to attain a near-lattice-matching conducive for lattice growth. Phase diagram for bandgap shows that as we increase the QW thickness, at a critical thickness, the electronic bandstructure switches from a normal to an inverted type. We confirm that such transition are topological phase transitions between a traditional insulator and a TI exhibiting QSH effect—by demonstrating the topologically protected edge-states using the bandstructure, edge-localized distribution of the wavefunctions and edge-state spin-momentum locking phenomenon, presence of non-zero conductance in spite of the Fermi energy lying in the bandgap window, crossover points of Landau levels in the zero-mode indicating topological band inversion in the absence of any magnetic field and presence of large Rashba spin-splitting, which is essential for spin-manipulation in TIs.

  12. Analytical Expressions of the Order Parameters Near the Transition Temperatures in the SPIN-3/2 Ising System with Bilinear and Biquadratic Interactions

    Science.gov (United States)

    Canko, Osman; Keskin, Mustafa

    Analytical expressions of the order parameters near the transition temperatures in the spin-3/2 Ising system with bilinear (J) and biquadratic (K) interactions are presented for various values of J/K. First, we obtain the free energy expression and the equations to determine order parameters by using the mean-field approximation. Then, the order parameters are expressed in the vicinity of the transition temperatures in which these expressions are very important to study the dynamics of the system by means of Onsager's theory of irreversible thermodynamics. Hence, we investigate the phase transitions occurring in the system and also obtain two tricritical points analytically. Finally, the specific heat and magnetic susceptibility are calculated and an argument about the critical exponents at the second-order phase transitions and tricritical points is given.

  13. Non-adiabatic Landau-Zener transitions in low-spin molecular magnet V sub 1 sub 5

    CERN Document Server

    Chiorescu, I; Müller, A; Bögge, H; Barbara, B

    2000-01-01

    The V sub 1 sub 5 polyoxovanadate molecule is made of 15 spins ((1)/(2)) with antiferromagnetic couplings. It belongs to the class of molecules with very large Hilbert space dimension (2 sup 1 sup 5 in V sub 1 sub 5 , 10 sup 8 in Mn sub 1 sub 2 -AC). It is a low spin/large molecule with spin S=((1)/(2)). Contrary to large spins/large molecules of the Mn sub 1 sub 2 -AC type, V sub 1 sub 5 has no energy barrier against spin rotation. Magnetization measurements have been performed and despite the absence of a barrier, magnetic hysteresis is observed over a timescale of several seconds. This new phenomenon characterized by a 'butterfly' hysteresis loop is due to the effect of the environment on the quantum rotation of the entangled 15 spins of the molecule, in which the phonon density of states is not at its equilibrium (phonon bottleneck).

  14. How does the spin-state of Co ions affect the insulator-metal transition in Bi2A2Co2O8 (A = Ca, Sr, Ba)?

    Science.gov (United States)

    Huang, Xiaokun; Zhang, Weiyi

    2016-11-01

    The misfit layered Bi2A2Co2O8 (A = Ca, Sr, Ba) compounds experience an insulator to metal transition as A’s ionic radius increases. This feature is contradictory to the conventional wisdom that larger lattice constant favors insulating rather than metallic state, and is also difficult to be reconciled using the Anderson weak localization theory. In this paper, we show from the first-principles calculation that an insulator-metal transition takes place from a nonmagnetic low-spin state of Co3+ ions to a hexagonally arranged intermediate-spin low-spin mixed-state in CoO2 plane when ionic radius increases from Ca to Ba. The predicted low-spin state of Bi2Ca2Co2O8 and Bi2Sr2Co2O8 and intermediate-spin low-spin mixed-state of Bi2Ba2Co2O8 are consistent not only with their measured transport properties, but also with the magnetic-field suppressed specific-heat peak observed at the transition temperature. In agreement with experiments, strong electronic correlation is required to stabilize the low-spin insulator and intermediate-spin low-spin metal.

  15. IR Studies of the Spin-Nuclear Conversion in the Vicinity of alpha α - beta β - Transition in Cryodeposited Methane Films

    Science.gov (United States)

    Drobyshev, A.; Aldiyarov, A.; Sokolov, D.; Shinbayeva, A.

    2017-06-01

    Solid methane belongs to a group of crystals containing hydrogen atoms, whose macroscopic properties are greatly influenced by the spin interaction of hydrogen nuclei. In particular, the methane molecule, which has four protons with spin I=1/2, has three total spin modifications: para-, ortho- and meta-states with three values of the total spin moments of 0, 1 and 2, respectively. Equilibrium concentrations of these modifications and relaxation times are dependent on the temperature, affecting the observed thermal properties of solid methane, such as thermal conductivity, specific heat, thermal expansion. In this paper, we attempt to explain the peculiarities of thin film growth of methane at cryogenic temperatures from the viewpoint of spin-nuclear transformations. Our observations of absorption intensity at a frequency corresponding to 1/2 of the absorption band amplitude of deformation vibrations record a step-like change in the position of the absorption band during the sample deposition process. The observed phenomenon, in our opinion, is the demonstration of spin transformations during deposition.

  16. Cerebral hemodynamic changes measured by gradient-echo or spin-echo bolus tracking and its correlation to changes in ICA blood flow measured by phase-mapping MRI

    DEFF Research Database (Denmark)

    Marstrand, J.R.; Rostrup, Egill; Garde, Ellen

    2001-01-01

    Changes in cerebral blood flow (CBF) induced by Acetazolamide (ACZ) were measured using dynamic susceptibility contrast MRI (DSC-MRI) with both spin echo (SE) EPI and gradient echo (GE) EPI, and related to changes in internal carotid artery (ICA) flow measured by phase-mapping. Also examined...... was the effect of repeated bolus injections. CBF, cerebral blood volume (CBV), and mean transit time (MTT) were calculated by singular value decomposition (SVD) and by deconvolution using an exponential function as kernel. The results showed no dependency on calculation method. GE-EPI measured a significant...... increase in CBF and CBV in response to ACZ, while SE-EPI measured a significant increase in CBV and MTT. CBV and MTT change measured by SE-EPI was sensitive to previous bolus injections. There was a significant linear relation between change in CBF measured by GE-EPI and change in ICA flow. In conclusion...

  17. Photo-Induced Spin-State Conversion in Solvated Transition Metal Complexes Probed via Time-Resolved Soft X-ray Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Huse, Nils; Kim, Tae Kyu; Jamula, Lindsey; McCusker, James K.; de Groot, Frank M. F.; Schoenlein, Robert W.

    2010-04-30

    Solution-phase photoinduced low-spin to high-spin conversion in the FeII polypyridyl complex [Fe(tren(py)3)]2+ (where tren(py)3 is tris(2-pyridylmethyliminoethyl)amine) has been studied via picosecond soft X-ray spectroscopy. Following 1A1 --> 1MLCT (metal-to-ligand charge transfer) excitation at 560 nm, changes in the iron L2- and L3-edges were observed concomitant with formation of the transient high-spin 5T2 state. Charge-transfer multiplet calculations coupled with data acquired on low-spin and high-spin model complexes revealed a reduction in ligand field splitting of 1 eV in the high-spin state relative to the singlet ground state. A significant reduction in orbital overlap between the central Fe-3d and the ligand N-2p orbitals was directly observed, consistent with the expected ca. 0.2 Angstrom increase in Fe-N bond length upon formation of the high-spin state. The overall occupancy of the Fe-3d orbitals remains constant upon spin crossover, suggesting that the reduction in sigma-donation is compensated by significant attenuation of pi-back-bonding in the metal-ligand interactions. These results demonstrate the feasibility and unique potential of time-resolved soft X-ray absorption spectroscopy to study ultrafast reactions in the liquid phase by directly probing the valence orbitals of first-row metals as well as lighter elements during the course of photochemical transformations.

  18. Thermally induced phase transitions and morphological changes in organoclays.

    Science.gov (United States)

    Gelfer, M; Burger, C; Fadeev, A; Sics, I; Chu, B; Hsiao, B S; Heintz, A; Kojo, K; Hsu, S L; Si, M; Rafailovich, M

    2004-04-27

    Thermal transitions and morphological changes in Cloisite organoclays were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, and in situ simultaneous small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) over the temperature range of 30-260 degrees C. On the basis of DSC and FTIR results, the surfactant component in organoclays was found to undergo a melting-like order-disorder transition between 35 and 50 degrees C. The transition temperatures of the DSC peaks (Ttr) in the organoclays varied slightly with the surfactant content; however, they were significantly lower than the melting temperature of the free surfactant (dimethyldihydrotallowammonium chloride; Tm = 70 degrees C). FTIR results indicated that within the vicinity of Ttr, the gauche content increased significantly in the conformation of surfactant molecules, while WAXD results did not show any change in three-dimensional ordering. Multiple scattering peaks were observed in SAXS profiles. In the SAXS data acquired below Ttr, the second scattering peak was found to occur at an angle lower than twice that of the first peak position (i.e., nonequidistant scattering maxima). In the data acquired above Ttr, the second peak was found to shift toward the equidistant position (the most drastic shift was seen in the system with the highest surfactant content). Using a novel SAXS modeling technique, we suggest that the appearance of nonequidistant SAXS maxima could result from a bimodal layer thickness distribution of the organic layers in organoclays. The occurrence of the equidistant scattering profile above Ttr could be explained by the conversion of the bimodal distribution to the unimodal distribution, indicating a redistribution of the surfactant that is nonbounded to the clay surface. At temperatures above 190 degrees C, the scattering maxima gradually broadened and became nonequidistant again but

  19. Do the transtheoretical processes of change predict transitions in stages of change for fruit intake?

    NARCIS (Netherlands)

    de Vet, E.W.M.L.; de Nooijer, J.; de Vries, N.K.; Brug, J.

    2008-01-01

    In a longitudinal study, it is examined whether the transtheoretical processes of change do predict stage transitions in fruit intake. A random sample of an existing Internet research panel resulted in a cohort of 735 adults, who were examined three times with electronic questionnaires assessing

  20. RHIC SPIN FLIPPER

    Energy Technology Data Exchange (ETDEWEB)

    BAI,M.; ROSER, T.

    2007-06-25

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

  1. Lattice dynamics, phase transitions and spin relaxation in [Fe(C{sub 5}H{sub 5}){sub 2}] PF{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Herber, R. H.; Felner, I.; Nowik, I., E-mail: nowik@vms.huji.ac.il [The Hebrew University, Racah Institute of Physics (Israel)

    2016-12-15

    The organometallic compound ferrocenium hexafluorophosphate, [Fe(C{sub 5}H{sub 5}){sub 2}] PF{sub 6}, has been studied by Mössbauer spectroscopy in the past, mainly to determine the crystal structure at high temperatures. Here we present studies at 95 K to 305 K and analyze the spectra in terms of spin relaxation theory which yields accurately the hyperfine interaction parameters and the spin-spin and spin-lattice relaxation rates in this paramagnetic compound. The spectral area under the resonance curve yields the recoil free fraction and thus the mean square of the vibration amplitude . One observes a large discontinuity in the slope of versus T at 210 K, indicative of a phase transition. The analysis of the spectra proves that the quadrupole interaction is small but certainly negative, ½e{sup 2}qQ = -0.12(2) mm/s, and causes the asymmetry observed in the spectra. The detailed analysis yields also, for the first time, the fluctuating effective magnetic hyperfine field, H {sub eff} = 180(50) kOe.

  2. Dynamics and control of dual-spin gyrostat spacecraft with changing structure

    Science.gov (United States)

    Aslanov, V. S.; Yudintsev, V. V.

    2013-01-01

    We study the motion of the free dual-spin gyrostat spacecraft that consists of the platform with a triaxial ellipsoid of inertia and the rotor with a small asymmetry with respect to the axis of rotation. The system with perturbations caused by a small asymmetry of the rotor and the time-varying moments of inertia of the rotor is considered. The dimensionless equations of the system are written in Serret-Andoyer canonical variables. The system's phase space is described. It is shown that changes in the moments of inertia of the gyrostat leads to the deformation of the phase space. The internal torque control law is proposed that keeps the system at the center point in the phase space. The effectiveness of the control is shown through a numerical simulation. It's shown that the uncontrolled gyrostat can lose its axis orientation. Proposed internal torque keeps the initial angle between the axis of the gyrostat and the total angular momentum vector.

  3. Investigation of spin-reorientation phase transitions at surface and in volume of alpha-Fe sub 2 O sub 3 monocrystals

    CERN Document Server

    Kamzin, A S

    2002-01-01

    The magnetic structure of the surface layer and volume and the processes, observed by the spin-reorientation phase transition (SRPT), are studied in the direct comparison of the properties of the thin surface layer and the volume of the hematite (alpha-Fe sub 2 O sub 3) macroscopic crystals. The method of simultaneous gamma, X-ray and electron Moessbauer spectroscopy was used in the studies. The direct data on the existence of the transition layer on the hematite crystals surface are obtained. It is established, that the Morin-type SRPT in the sample volume occurs by a jump (the first-order phase transition). The SRPT in the surface layer as well as in the crystal volume is accompanied by formation of the intermediate state, wherein the low- and high-temperature phases coexist. The obtained experimental data on the SRPT mechanism in the surface layer agree well with the conclusions of the phenomenological theory

  4. Anomalous spin waves and the commensurate-incommensurate magnetic phase transition in LiNiPO4

    DEFF Research Database (Denmark)

    Jensen, Thomas Bagger Stibius; Christensen, Niels Bech; Kenzelmann, M.

    2009-01-01

    Detailed spin-wave spectra of magnetoelectric LiNiPO4 have been measured by neutron scattering at low temperatures in the commensurate (C) antiferromagnetic (AF) phase below T-N=20.8 K. An anomalous shallow minimum is observed at the modulation vector of the incommensurate (IC) AF phase appearing...... above T-N. A linear spin-wave model based on Heisenberg exchange couplings and single-ion anisotropies accounts for all the observed spin-wave dispersions and intensities. Along the b axis an unusually strong next-nearest-neighbor AF coupling competes with the dominant nearest-neighbor AF exchange...

  5. A vulnerability and risk assessment of SEPTA's regional rail : a transit climate change adaptation assessment pilot.

    Science.gov (United States)

    2013-08-01

    This final report for the Federal Transit Administration (FTA) Transit Climate Change Adaptation Assessment Pilot describes the actions : taken, information gathered, analyses performed, and lessons learned throughout the pilot project. This report d...

  6. Spin-orbit angle measurements for six southern transiting planets: New insights into the dynamical origins of hot Jupiters

    National Research Council Canada - National Science Library

    Triaud, A. H. M. J; Collier Cameron, A; Queloz, D; Anderson, D. R; Gillon, M; Hebb, L; Hellier, C; Loeillet, B; Maxted, P. F. L; Mayor, M; Pepe, F; Pollacco, D; Ségransan, D; Smalley, B; Udry, S; West, R. G; Wheatley, P. J

    2010-01-01

    .... Our goal is to measure the degree of alignment between planetary orbits and stellar spin axes, to search for potential correlations with eccentricity or other planetary parameters and to measure long...

  7. Spin Orbit Torque in Ferromagnetic Semiconductors

    KAUST Repository

    Li, Hang

    2016-06-21

    effect on spin orbit torque in nanoribbons with a hexagonal lattice. We find a dramatic modification of the nature of the torque (field like and damping-like component) when crossing the topological phase transition. The relative agnitude of the two torque components can be significantly modifies by changing the magnetization direction. Finally, motivated by recent experimental results, we conclude by investigating the features of spin-orbit torque in magnetic transition metal dichalcogenides. We find the torque is associated with the valley polarization. By changing the magnetization direction, the torque can be changed from a finite value to zero when the valley polarization decreases from a finite value to zero.

  8. Study of the first-order transition in the spin-1 Blume–Capel model by using effective-field theory

    Energy Technology Data Exchange (ETDEWEB)

    Costabile, Emanuel [Departamento de Física, Universidade Federal do Amazonas, 3000, Japiim, 69077-000, Manaus, AM (Brazil); Amazonas, Marcio A. [Departamento de Física, Universidade Federal do Amazonas, 3000, Japiim, 69077-000, Manaus, AM (Brazil); Instituto Federal de Educação, Ciência e Tecnologia do Amazonas, 1975, Sete de Setembro, 69020-120, Manaus, AM (Brazil); Viana, J. Roberto [Departamento de Física, Universidade Federal do Amazonas, 3000, Japiim, 69077-000, Manaus, AM (Brazil); Sousa, J. Ricardo de, E-mail: jsousa@ufam.edu.br.br [Departamento de Física, Universidade Federal do Amazonas, 3000, Japiim, 69077-000, Manaus, AM (Brazil); National Institute of Science and Technology for Complex Systems, Universidade Federal do Amazonas, 3000, Japiim, 69077-000, Manaus, AM (Brazil)

    2012-10-01

    The spin-1 Blume–Capel model on a square lattice is studied by using an effective-field theory (EFT) with correlation. We propose an expression for the free energy within the EFT. The phase diagram is constructed in the temperature (T) and single-ion anisotropy amplitude (D) plane. The first-order transition line is obtained by Maxwell construction (comparison between free energies). Our results predict first-order transitions at low temperatures and large anisotropy strengths, which correspond in the phase diagram to the existence of a tricritical point (TCP). We compare our results with mean-field approximation (MFA), that show a qualitative correct behavior for the phase diagram. -- Highlights: ► In this Letter we have studied the spin-1 Blume–Capel model by using effective-field theory (EFT). ► The first-order line is obtained for the first time. ► The model presents second and first-order phase transitions. ► We propose a functional to treat the first-order line. ► We discuss other alternative by using EFT to study first-order line.

  9. Neutron powder diffraction investigation of magnetic structure and spin reorientation transition of HoFe{sub 1-x}Cr{sub x}O{sub 3} solid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xinzhi [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China); Hao, Lijie, E-mail: haolijie@ciae.ac.cn [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China); Liu, Yuntao; Ma, Xiaobai; Meng, Siqin; Li, Yuqing; Gao, Jianbo; Guo, Hao; Han, Wenze; Sun, Kai; Wu, Meimei [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China); Chen, Xiping; Xie, Lei [Institute of Nuclear Physics and Chemistry, CAEP, Mianyang 621900 (China); Klose, Frank [Australian Nuclear Science and Technology Organization, Lucas Heights, New South Wales 2234 (Australia); Department of Physics and Materials Science, The City University of Hong Kong, Hong Kong (China); Chen, Dongfeng, E-mail: dongfeng@ciae.ac.cn [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China)

    2016-11-01

    Orthoferrite solid solution HoFe{sub 1−x}Cr{sub x}O{sub 3} (x=0, 0.2,…,1.0) was synthesized via solid state reaction methods. The crystal structure, magnetism and spin reorientation properties of this system were investigated by X-ray diffraction, neutron powder diffraction and magnetic measurements. For compositions of x≤0.6, the system exhibits similar magnetic properties to HoFeO{sub 3}. With increasing Cr-doping, the system adopts a Γ{sub 4}(G{sub x}A{sub y}F{sub z}) magnetic configuration with a decreased Neel temperature from 640 K to 360 K. A Γ{sub 42} spin reorientation of Fe(Cr){sup 3+} was also observed in this system with an increase in transition temperature from 56 K to about 200 K due to competition between the Fe(Cr)–Fe(Cr) and Ho–Fe(Cr) interactions. For the x≥0.8, the system behaves more like HoCrO{sub 3} which adopts a Γ{sub 2}(F{sub x}C{sub y}G{sub z}) configuration with no spin reorientation below the Neel temperature T{sub N}. Throughout the whole substitution range, we found that the saturated moment of Fe(Cr) was less than the ideal value for a free ion, which implies the existence of spin fluctuation in this system. A systematic magnetic structure variation with Cr-substitution is revealed by Rietveld refinement. A phase diagram combining the results of the magnetic measurements and neutron powder diffraction results was obtained. - Highlights: • With Cr-substitution in the HoFe{sub 1−x}Cr{sub x}O{sub 3} system, A Γ{sub 42} spin reorientation of Fe(Cr){sup 3+} was observed with an increase in transition temperature from 56 K to about 200 K for x=0−0.6. • The saturated moment of Fe(Cr) position was found to be systematically less than the ideal value of free ion, and thus implies the presence of spin quantum fluctuation. • A composition–temperature phase diagram throughout x=0–1 for HoFe{sub 1−x}Cr{sub x}O{sub 3} system was established.

  10. Momentum-space spin texture in a topological superconductor

    Science.gov (United States)

    Loder, Florian; Kampf, Arno P.; Kopp, Thilo; Braak, Daniel

    2017-07-01

    A conventional superconductor with spin-orbit coupling turns into a topological superconductor beyond a critical strength of the Zeeman energy. The spin-expectation values S (k ) in momentum space trace this transition via a characteristic change in the topological character of the spin texture within the Brillouin zone. At the transition the skyrmion counting number switches from 0 to 1/2 identifying the topological superconductor via its meron-like spin texture. The change in the skyrmion counting number is crucially controlled by singular points of the map S (k )/|S (k )| from the Brillouin zone, i.e., a torus, to the unit sphere. The complexity of this spin map is discussed at zero temperature as well as for the extension to finite temperatures.

  11. Momentum-space spin texture of a topological superconductor

    Science.gov (United States)

    Kampf, Arno; Loder, Florian; Kopp, Thilo; Braak, Daniel

    A conventional superconductor with spin-orbit coupling turns into a topological superconductor beyond a critical strength of the Zeeman coupling. The spin-expectation values S (k) in momentum space trace this transition via a characteristic change in the topological character of the spin texture within the Brillouin zone. At the transition the skyrmion counting number switches from 0 to 1/2 identifying the topological superconductor via its meron-like spin texture. The change in the skyrmion counting number is crucially controlled by singular points of the map S (k) / | S (k) | from the Brillouin zone, i.e. a torus, to the unit sphere. The complexity of this spin-map is discussed at zero temperature as well as for the extension to finite temperatures. Supported by the DFG through TRR 80.

  12. Application of an automatic yarn dismantler to track changes in cotton fibre properties during processing on a miniature spinning line

    CSIR Research Space (South Africa)

    Fassihi, A

    2014-11-01

    Full Text Available This paper reports on the application of a newly developed automatic yarn dismantler for dismantling short staple ring-spun yarns, to track changes in cotton fibre properties from lint to yarn, during processing on a miniature spinning line...

  13. Preparation and performance of novel polyvinylpyrrolidone/polyethylene glycol phase change materials composite fibers by centrifugal spinning

    Science.gov (United States)

    Zhang, Xiaoguang; Qiao, Jiaxin; Zhao, Hang; Huang, Zhaohui; Liu, Yangai; Fang, Minghao; Wu, Xiaowen; Min, Xin

    2018-01-01

    Currently, phase change materials (PCMs) composite fibers are typically prepared by electrospinning. However, electrospinning exhibits safety concerns and a low production rate, which limit its practical applications as a cost-effective fiber fabrication approach. Therefore, a novel, and simple centrifugal spinning technology is employed to extrude fibers from composite solutions using a high-speed rotary and perforated spinneret. The composite fibers based on polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) were prepared by centrifugal spinning. The SEM of PVP/PEG composite fibers indicated that the fibrous morphology is well preserved. The DSC and TGA indicated that PVP/PEG composite fibers exhibit good thermal properties.

  14. Influence of the spin quantum number $s$ on the zero-temperature phase transition in the square lattice $J$-$J'$ model

    OpenAIRE

    Darradi, R.; Richter, J.; Farnell, D. J. J.

    2004-01-01

    We investigate the phase diagram of the Heisenberg antiferromagnet on the square lattice with two different nearest-neighbor bonds $J$ and $J'$ ($J$-$J'$ model) at zero temperature. The model exhibits a quantum phase transition at a critical value $J'_c > J$ between a semi-classically ordered N\\'eel and a magnetically disordered quantum paramagnetic phase of valence-bond type, which is driven by local singlet formation on $J'$ bonds. We study the influence of spin quantum number $s$ on this p...

  15. Spin period change and the magnetic fields of neutron stars in Be X-ray binaries in the SMC

    Directory of Open Access Journals (Sweden)

    Klus H.

    2014-01-01

    Full Text Available We report on the long term average spin period, rate of change of spin period and X-ray luminosity during outbursts for 42 Be X-ray binary systems in the Small Magellanic Cloud. We also collect and calculate parameters of each system and use this data to determine that all systems contain a neutron star which is accreting via a disc, rather than a wind, and that if these neutron stars are near spin equilibrium, then over half of them, including all with spin periods over about 100 seconds, have magnetic fields over the quantum critical level of 4.4×1013 G. If these neutron stars are not close to spin equilibrium, then their magnetic fields are inferred to be much lower, on the order of 106-1010 G, comparable to the fields of neutron stars in low mass X-ray binaries. Both results are unexpected and have implications for the rate of magnetic field decay and the isolated neutron star population.

  16. Agents of Change: Interpreters as Witnesses of Transition

    Directory of Open Access Journals (Sweden)

    Kristina Mullamaa

    2014-08-01

    Full Text Available In this article we would like to share the preliminary results of our on-going research on the memories of interpreters. From 2011-2012 we have carried out in-depth interviews with representatives of two different samples: experienced dialogue interpreters a in Estonia and  b in Sweden, most of whom have worked from the 1960s till today. This article sums up the preliminary results on the sample from Estonia. The focus is on the development of the interpreter´s role as reflecting the changes in society, cultural and social practices. As for the theoretical background, we view the processes within the framework of Transition Studies (cf. Lauristin, Vihalemm 2010;  Kennedy 2002. The methodological framework is ethnographic research. More specifically:  we combine narrative studies and memory research ( Kõresaar, Kirss 2004; Riessman 1993, Middleton, Brown 2005, Gilbert 2008; method:  semi-structured interviews (cf. Nunan 1992, Van Maanen 1983, Gilbert 2008. The analysis of our on-going research also enables us to test and share with our readers the pros and cons of the chosen methodology and methods.

  17. Rethinking Healthcare Transitions and Policies: Changing and Expanding Roles in Transitional Care

    Science.gov (United States)

    Moreño, Patricienn K.

    2014-01-01

    The breakdown of care transitions between various healthcare facilities, providers, and services is a major issue in healthcare, and accounts for over US$15 billion in healthcare expenditures annually. The transition between inpatient care and home care is a very delicate period where, too often, chronically ill patients get worse and wind up back…

  18. Transition? What transition? : Changing energy systems in an increasingly carbon constrained world

    NARCIS (Netherlands)

    Mc Cahery, J.A.; Lopez de Silanes, Florencio; de Roode, Alexander

    2014-01-01

    Energy transitions have been taking place continuously since the Industrial Revolution. These transitions primarily involve national energy mixes. In general, countries keep moving up the energy ladder, meaning that they integrate larger and larger proportions of specialized fuels into their energy

  19. Boards and Leadership Change: The Pitfalls of Involuntary Headship Transitions

    Science.gov (United States)

    Wilson, Debra P.

    2015-01-01

    Head of school transitions happen for a variety of reasons. Without a doubt, however, the most stressful ones are those that are not voluntary. In the last few years, an increasing number of boards have decided to let their heads go at nontraditional transition times. In turn, this has left the school leadership staff scrambling to ensure that the…

  20. Changes in the excitations related to the superconducting transition ...

    Indian Academy of Sciences (India)

    superconducting transition in V3Si. M YETHIRAJ. Bragg Institute, ANSTO, Lucas Heights, NSW 2234, Australia. E-mail: mohana.yethiraj@gmail.com. Abstract. In earlier studies of phonons in V3Si, a gradual softening of the (h h 0) branch was observed and attributed to the martensitic transition in this compound, which pre-.

  1. Rural Agricultural Change and Fertility Transition in Nepal

    Science.gov (United States)

    Bhandari, Prem; Ghimire, Dirgha

    2013-01-01

    Using longitudinal panel data from the Western Chitwan Valley of Nepal, this study examines the impact of the use of modern farm technologies on fertility transition--specifically, the number of births in a farm household. Previous explanations for the slow pace of fertility transition in rural agricultural settings often argued that the demand…

  2. Spin-driven pyroelectricity in Ni{sub 3}TeO{sub 6} without ferroelectric signatures of the transition at Neel temperature

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, L.; Komarek, A.C. [Max-Planck-Institute for Chemical Physics of Solids, Dresden (Germany); Du, C.H. [Department of Physics, Tamkang University, Tamsui, Taiwan (China)

    2017-07-15

    Here we report on dielectric studies on Ni{sub 3}TeO{sub 6}. We confirm the spin-driven pyroelectric transition at the Neel temperature (T{sub N}) of ∝52.5 K. The measurement of single crystalline and polycrystalline samples excludes a ferroelectric nature of the transition at T{sub N} in this compound. The excellent pyroelectric properties without any intrinsic ferroelectric hysteresis make Ni{sub 3}TeO{sub 6} appropriate for applications in future devices. Pyroelectric measurements on our Ni{sub 3}TeO{sub 6} single crystals. The polarization that appears on cooling through T{sub N} can not be inverted by opposite poling fields (applied when cooling from above T{sub N} to base temperature). (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Surface-induced spin state locking of the [Fe(H2B(pz)2)2(bipy)] spin crossover complex

    Science.gov (United States)

    Beniwal, S.; Zhang, X.; Mu, S.; Naim, A.; Rosa, P.; Chastanet, G.; Létard, J.-F.; Liu, J.; Sterbinsky, G. E.; Arena, D. A.; Dowben, P. A.; Enders, A.

    2016-05-01

    Temperature- and coverage-dependent studies of the Au(1 1 1)-supported spin crossover Fe(II) complex (SCO) of the type [Fe(H2B(pz)2)2(bipy)] with a suite of surface-sensitive spectroscopy and microscopy tools show that the substrate inhibits thermally induced transitions of the molecular spin state, so that both high-spin and low-spin states are preserved far beyond the spin transition temperature of free molecules. Scanning tunneling microscopy confirms that [Fe(H2B(pz)2)2(bipy)] grows as ordered, molecular bilayer islands at sub-monolayer coverage and as disordered film at higher coverage. The temperature dependence of the electronic structure suggest that the SCO films exhibit a mixture of spin states at room temperature, but upon cooling below the spin crossover transition the film spin state is best described as a mix of high-spin and low-spin state molecules of a ratio that is constant. This locking of the spin state is most likely the result of a substrate-induced conformational change of the interfacial molecules, but it is estimated that also the intra-atomic electron-electron Coulomb correlation energy, or Hubbard correlation energy U, could be an additional contributing factor.

  4. Spin injection and spin transport in paramagnetic insulators

    OpenAIRE

    Okamoto, Satoshi

    2016-01-01

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

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

    Science.gov (United States)

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

    2014-06-01

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

  6. Formation of gapless Z 2 spin liquid phase manganites in the (Sm1- y Gd y )0.55Sr0.45MnO3 system in zero magnetic field: Topological phase transitions to states with low and high density of 2D-vortex pairs induced by the magnetic field

    Science.gov (United States)

    Bukhan'ko, F. N.; Bukhan'ko, A. F.

    2017-12-01

    The evolution of the ground state of the manganese spin ensemble in the (Sm1- y Gd y )0.55Sr0.45MnO3 in the case of isovalent substitution of rare-earth samarium ions with large radii with gadolinium ions with significantly smaller radii is studied. The measured temperature dependences of the ac magnetic susceptibility and the field dependences of the dc magnetizations are analyzed using the Heisenberg-Kitaev model describing the transition from the ordered spin state with classical isotropic AFM exchange to the frustrated spin state with quantum highly anisotropic FM exchange. A continuous transition from the 3D ferromagnetic state of manganese spins in the initial sample with y = 0 to zigzag AFM ordering of CE-type spins in ab planes for y = 0.5, coexisting in samples with y = 0.5, 0.6, and 0.7 at temperatures below T N ≅ 48.5 K with a disordered phase such as a quantum Griffiths phase is identified. As the gadolinium concentration further increases, the CE-type zigzag AFM structure is molten, which leads to the appearance of an unusual phase in Gd0.55Sr0.45MnO3 in the temperature range close to the absolute zero. This phase has characteristic features of a gapless Z 2 quantum spin liquid in zero external magnetic field. The step changes in the magnetization isotherms measured at 4.2 K in the field range of ±75 kOe are explained by quantum phase transitions of the Z 2 spin liquid to a phase with topological order in weak magnetic fields and a polarized phase in strong fields. The significant difference between critical fields and magnetization jumps in isotherms indicates the existence of hysteretic phenomena in quantum spin liquid magnetization-demagnetization processes caused by the difference between localization-delocalization of 2D vortex pairs induced by a magnetic field in a quantum spin liquid with disorder.

  7. Prescription for change: accessing medication in transitional Russia.

    Science.gov (United States)

    Perlman, Francesca; Balabanova, Dina

    2011-11-01

    BACKGROUND Many Russians experienced difficulty in accessing prescription medication during the widespread health service disruption and rapid socio-economic transition of the 1990s. This paper examines trends and determinants of access in Russia during this period. METHODS Data were from nine rounds (1994-2004) of the Russia Longitudinal Monitoring Survey, a 38-centre household panel survey. Trends were measured in failing to access prescribed medication for the following reasons: unobtainable from a pharmacy, unable to afford and 'other' reasons. Determinants of unaffordability were studied in 1994, 1998 and 2004, using cross-sectional, age-adjusted logistic regression, with further multivariate analyses of unaffordability and failure to access for 'other' reasons in 2004. RESULTS After 1994, reporting of unavailability in pharmacies fell sharply from 25% to 4%. Meanwhile, unaffordability increased to 20% in 1998 but declined to 9% by 2004. In 1994, significant determinants of unaffordability were unemployment and lacking health care insurance in men. By 2004, determinants included low income and material goods in both sexes; rented accommodation and low education in men; and chronic disease and disability-related retirement in women. Not obtaining medicines for 'other' reasons was more likely amongst frequent male drinkers, and low educated or cohabiting women. Regional and gender differences were widest in 1998, coinciding with the Russian financial crisis. CONCLUSIONS Rapid improvements in drug availability in the late 1990s in Russia are a probable consequence of a more liberalized pharmaceutical sector and an improved pharmacy network, whilst later improvements in affordability may relate to expanded health care insurance coverage and economic recovery after the 1998 crash. A significant minority still finds prescription costs problematic, notably poorer and sick individuals, with inequalities apparently widening. Non-monetary determinants of affordability

  8. Transit climate change adaptation assessment/asset management pilot for the Metropolitan Atlanta Rapid Transit Authority.

    Science.gov (United States)

    2013-08-01

    Public transit agencies play an important role in the provision of safe, reliable, and cost-effective transportation for the communities they serve. With the growing intensity and frequency of extreme weather events, such as hurricanes Irene and Sand...

  9. Investigation of Quantum Phase Transitions of Spin-3/2 AKLT Systems On the Hexagonal Lattice via the Tensor-Network Method

    Science.gov (United States)

    Wei, Tzu-Chieh; Huang, Ching-Yu

    The spin-3/2 Affleck-Kennedy-Lieb-Tasaki (AKLT) state on the hexagonal lattice is an example of valence-bond solid state (VBS), which is recently shown to provide resource for quantum computation and is also a nontrivial symmetry protected topologically ordered state if the translation invariance is imposed in addition to the rotation symmetry. Niggemann et al. previously studied a deformation of the AKLT model and derived a one-parameter family of ground states (parametrized by a) that are deformed from the AKLT point (a =√{ 3}). By mapping to a free-fermion eight-vertex model, they identified a VBS to Néel transition at ac 2 2 . 5425 . We employ the tensor-network method to directly compute the Néel order parameter and obtain results that agree with theirs. We also study the regime where the deformation parameter a decreases close to zero. We find that there is a transition at ac 1 0 . 58 to an XY phase, which is characterized by algebraically decaying correlations, rotation invariance of spins in the x-y plane and the induced magnetization being aligned with the direction of the extend field. This work was supported in part by the National Science Foundation.

  10. Highly frustrated spin-lattice models of magnetism and their quantum phase transitions: A microscopic treatment via the coupled cluster method

    Science.gov (United States)

    Bishop, R. F.; Li, P. H. Y.; Campbell, C. E.

    2014-10-01

    We outline how the coupled cluster method of microscopic quantum many-body theory can be utilized in practice to give highly accurate results for the ground-state properties of a wide variety of highly frustrated and strongly correlated spin-lattice models of interest in quantum magnetism, including their quantum phase transitions. The method itself is described, and it is shown how it may be implemented in practice to high orders in a systematically improvable hierarchy of (so-called LSUBm) approximations, by the use of computer-algebraic techniques. The method works from the outset in the thermodynamic limit of an infinite lattice at all levels of approximation, and it is shown both how the "raw" LSUBm results are themselves generally excellent in the sense that they converge rapidly, and how they may accurately be extrapolated to the exact limit, m → ∞, of the truncation index m, which denotes the only approximation made. All of this is illustrated via a specific application to a two-dimensional, frustrated, spin-half J1XXZ-J2XXZ model on a honeycomb lattice with nearest-neighbor and next-nearest-neighbor interactions with exchange couplings J1 > 0 and J2 ≡ κJ1 > 0, respectively, where both interactions are of the same anisotropic XXZ type. We show how the method can be used to determine the entire zero-temperature ground-state phase diagram of the model in the range 0 ≤ κ ≤ 1 of the frustration parameter and 0 ≤ Δ ≤ 1 of the spin-space anisotropy parameter. In particular, we identify a candidate quantum spin-liquid region in the phase space.

  11. Accuracy of the spin sum rule in XMCD for the transition-metal L edges from manganese to copper

    NARCIS (Netherlands)

    Piamonteze, Cinthia; Miedema, Piter; de Groot, Frank M. F.

    2009-01-01

    The effective spin sum rule is widely used in the quantitative analysis of x-ray magnetic circular dichroism spectra. Here, this important, though imperfect, sum rule is reviewed with a detailed analysis of the various sources for errors and deviations. The simulations confirm that the final state

  12. Resilience, Regime Shifts, and Guided Transition under Climate Change: Examining the Practical Difficulties of Managing Continually Changing Systems

    Directory of Open Access Journals (Sweden)

    Brenda B. Lin

    2013-03-01

    Full Text Available Managing terrestrial systems has become increasingly difficult under climate change as unidirectional shifts in climate conditions challenge the resilience of ecosystems to maintain their compositional structure and function. Despite the increased attention of resilience management to guide transformational change, questions remain as to how to apply resilience to manage transitions. Rather than pushing systems across thresholds into alternative states, climate change may create a stepwise progression of unknown transitional states that track changing climate conditions. Because of this uncertainty, we must find ways to guide transitioning systems across climate boundaries towards states that are socially and environmentally desirable. We propose to ease the uncertainty of managing shifting systems by providing an approach to adaptive management that we call guided transition, where socially and environmentally important ecosystem functions are preserved through transitions by considering and maintaining the species and structures needed for the desired functions. Scientifically, it will require a better understanding of the relationships between structure, species composition, and function for specific systems. Managers will also need to identify important functions at the local, regional, and national scale, and to determine how best to transition systems to a desired state based on existing scientific knowledge. Guided transition, therefore, helps guide the process of adaptive management by specifying a function-based management pathway that guides transitions through climatic changes.

  13. Shape change as entropic phase transition: A study using Jarzynski ...

    Indian Academy of Sciences (India)

    Abstract. A Brownian particle in a confined space with varying cross-section, experiences an effective entropic potential in reduced dimension. We modulate the shape of the confinement and examine the nature of dynamical transition between two distinct thermalized entropic states corresponding to different shapes of the.

  14. Changes and challenges: China's environmental management in transition

    NARCIS (Netherlands)

    He, G.; Lu, Y.; Mol, A.P.J.; Beckers, T.A.M.

    2012-01-01

    China's 12th Five-Year Plan (2011–2015) announces a shift to a new development model and a new green governance approach. Can we indeed identify a specific Chinese transition mode in moving from a monolithic economic growth path to a sincere green development model? To understand China's

  15. Changes in the Earth’s Spin Rotation due to the Atmospheric Effects and Reduction in Glaciers

    Directory of Open Access Journals (Sweden)

    Sung-Ho Na

    2016-12-01

    Full Text Available The atmosphere strongly affects the Earth’s spin rotation in wide range of timescale from daily to annual. Its dominant role in the seasonal perturbations of both the pole position and spinning rate of the Earth is once again confirmed by a comparison of two recent data sets; i the Earth orientation parameter and ii the global atmospheric state. The atmospheric semi-diurnal tide has been known to be a source of the Earth’s spin acceleration, and its magnitude is re-estimated by using an enhanced formulation and an up-dated empirical atmospheric S2 tide model. During the last twenty years, an unusual eastward drift of the Earth’s pole has been observed. The change in the Earth’s inertia tensor due to glacier mass redistribution is directly assessed, and the recent eastward movement of the pole is ascribed to this change. Furthermore, the associated changes in the length of day and UT1 are estimated.

  16. Value stability and change during self-chosen life transitions: self-selection versus socialization effects.

    Science.gov (United States)

    Bardi, Anat; Buchanan, Kathryn E; Goodwin, Robin; Slabu, Letitia; Robinson, Mark

    2014-01-01

    Three longitudinal studies examine a fundamental question regarding adjustment of personal values to self-chosen life transitions: Do values fit the new life setting already at its onset, implying value-based self-selection? Or do values change to better fit the appropriate and desirable values in the setting, implying value socialization? As people are likely to choose a life transition partly based on their values, their values may fit the new life situation already at its onset, leaving little need for value socialization. However, we propose that this may vary as a function of the extent of change the life transition entails, with greater change requiring more value socialization. To enable generalization, we used 3 longitudinal studies spanning 3 different life transitions and different extents of life changes: vocational training (of new police recruits), education (psychology vs. business students), and migration (from Poland to Britain). Although each life transition involved different key values and different populations, across all 3 studies we found value fit to the life situation already early in the transition. Value socialization became more evident the more aspects of life changed as part of the transition, that is, in the migration transition. The discussion focuses on the implications of these findings for research on values and personality change, as well as limitations and future directions for research.

  17. Glass transition-related changes in molecular mobility below glass transition temperature of freeze-dried formulations, as measured by dielectric spectroscopy and solid state nuclear magnetic resonance.

    Science.gov (United States)

    Yoshioka, Sumie; Aso, Yukio

    2005-02-01

    The purpose of this study was to explore why changes in the molecular mobility associated with glass transition, the timescale of which is on the order of 100 s, can be detected by measuring the nuclear magnetic resonance relaxation times that reflect molecular motions on the order of 10 kHz and 1 MHz. The molecular motions in freeze-dried dextran 40k, dextran 1k, isomaltotriose (IMT), and alpha-glucose comprising a common unit but with different glass transition temperatures, were investigated by dielectric spectroscopy (DES) in the frequency range of 0.01 Hz to 100 kHz and in the temperature range of -20 degrees to 200 degrees C, in order to compare with the molecular motions reflected in nuclear magnetic resonance relaxation times. The alpha-relaxation process for freeze-dried alpha-glucose was visualized by DES, whereas those for freeze-dried dextran 40k, dextran 1k, and IMT were too slow to be visualized by DES. The latter freeze-dried cakes exhibited quasi-dc polarization because of proton-hopping-like motion rather than alpha-relaxation process. The correlation time (tau(c)) for the backbone carbon of dextran 40k and IMT, calculated from the measured value of spin-lattice relaxation time in the rotating frame, was found to be close to the relaxation time of proton-hopping-like motion determined by DES (tau(DES)) at temperatures around glass transition temperature. The timescales of molecular motions reflected in the tau(c) and tau(DES) were significantly smaller than that of motions leading to molecular rearrangement (molecular rearrangement motions), which correspond to alpha-relaxation. However, the shapes of temperature dependence for the tau(c) and tau(DES) were similar to that of the calorimetrically determined relaxation time of molecular rearrangement motions. Results suggest that the molecular motions reflected in the tau(c) and tau(DES) are linked to molecular rearrangement motions, such that enhancement of molecular rearrangement motions enhances

  18. Many-body and spin-orbit effects on direct-indirect band gap transition of strained monolayer MoS{sub 2} and WS{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Luqing; Kutana, Alex [Department of Materials Science and Nanoengineering, Rice University, Houston, TX (United States); Yakobson, Boris I. [Department of Materials Science and Nanoengineering, Rice University, Houston, TX (United States); Department of Chemistry, Rice University, Houston, TX (United States); Smalley Institute for Nanoscale Science and Technology, Rice University, Houston, TX (United States)

    2014-10-15

    Monolayer transition metal dichalcogenides are promising materials for photoelectronic devices. Among them, molybdenum disulphide (MoS{sub 2}) and tungsten disulphide (WS{sub 2}) are some of the best candidates due to their favorable band gap values and band edge alignments. Here, various perturbative corrections to the DFT electronic structure, e.g. GW, spin-orbit coupling, as well as many-body excitonic and trionic effects are considered, and accurate band gaps as a function of homogeneous biaxial strain in these materials are calculated. All of these corrections are shown to be of comparable magnitudes and need to be included in order to obtain an accurate electronic structure. The strain at which the direct-to-indirect gap transition occurs is calculated. After considering all contributions, the direct to indirect gap transition strain is predicted to be at 2.7% in MoS{sub 2} and 3.9% in WS{sub 2}. These values are generally higher than the previously reported theoretical values. (copyright 2014 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Hydrostatic pressure effect on the spin reorientation transition of ferromagnetic Sm0.7-xLaxSr0.3MnO3 (x = 0, 0.1) polycrystals

    Science.gov (United States)

    Thiyagarajan, R.; Arumugam, S.; Sivaprakash, P.; Kannan, M.; Saravanan, C.; Yang, Wenge

    2017-06-01

    The hydrostatic pressure effect on the resistivity and magnetization of the narrow band gap manganite Sm0.7-xLaxSr0.3MnO3 (x = 0, 0.1) systems has been investigated. At ambient pressure measurements, the parent compound Sm0.7Sr0.3MnO3 showed a ferromagnetic-insulating nature, whereas the 10% La-doped compound Sm0.6La0.1Sr0.3MnO3 showed a ferromagnetic-metallic nature. Furthermore, both samples showed a spin-reorientation transition (TSR) below Curie temperature, which originated from the Mn sublattice and was supported by an antiferromagnetic Sm(4f)-Mn(3d) interaction. Both samples exhibited a normal and inverse magnetocaloric effect as a result of these two different magnetic transitions. Magnetization measurements on Sm0.7Sr0.3MnO3 under pressure did not show an appreciable change in the Curie temperature, but enhanced TSR, whereas an insulator-metallic transition was observed during resistivity measurements under pressure. On the other hand, for Sm0.6La0.1Sr0.3MnO3, TC increased and TSR reduced upon the application of pressure. The metallic nature which is observed at ambient pressure resistivity measurement was further enhanced with 97% of piezoresistance. The pressure did not change the normal magnetocaloric effect of Sm0.7Sr0.3MnO3, but increased it in Sm0.6La0.1Sr0.3MnO3. However, there was not much change in the inverse magnetocaloric effect of both compounds. These studies were analyzed based on the pressure effect on the activation energy and scattering interaction factors.

  20. Women's Employment Transitions and Changes in Psychological Distress

    Directory of Open Access Journals (Sweden)

    Wilk, Piotr

    2001-01-01

    Full Text Available EnglishThe effect of employment on women's psychological well being has become animportant issue in the sociology of mental health. Although work-for-pay is thought to have an overallpostiive impact on women's psychological well being, not all women equally experience this positiveeffect. The objective of this study is to assess the effect of transitions in employment status onchanges in psychological distress among women in two types of family setting: lone parent families andmarried couple families (including common-law unions. Using a framework which combines a longitudinaldesign with a structural equation modelling multigroup analysis, the current study indicates clearlythat the employment transitions and employment stability have no uniform effect on the mental healthof all mothers. Specifically, transition into employment offers a significant reduction in feelings ofdistress only among married mothers. Single mothers, in contrast are found to experience a significantincrease in the level of distress when they move out of employment. The results of this study point tosome advantages of longitudinal research designs over cross-section designs.FrenchL'effet de l'emploi sur le bien-être psychologique des femmes est devenu unequestion importante en sociologie de santé mentale. Bien que le travail payé aitun impact positif global sur le bien-être psychologique des femmes, pas toutesles femmes éprouvent également cet effet positif. L'objectif de cette étude estd'évaluer l'effet des transitions dans le statut d'emploi sur des changements de ladétresse psychologique parmi des femmes dans deux types de famille: famillesà un seul parent et familles à couple mariés (y compris les mariages de fait. Enutilisant un cadre qui combine une analyse longitudinale avec une équationstructurale modelant plusieurs groupes, l'étude actuelle indique clairement queles transitions d'emploi et la stabilité d'emploi n'ont pas un effet uniforme sur lasant

  1. Leading Change: Transitioning the AFMS into a High Reliability Organization

    Science.gov (United States)

    2016-02-16

    behavior is similar to a 7 traditional vertical organization, a culture comfortable with stability and resistant to change , having its own values...the change is, why the company needs to change , and how implementation will affect them.31 Resistance to change also occurs when leaders fail to...Employees want to know when the change is going to occur; lack of details leads to speculation and rumor, causing concern and workplace disruption

  2. Energy Transitions, Economic Growth and Structural Change: Portugal in a Long-run Comparative Perspective

    OpenAIRE

    Henriques, Sofia

    2011-01-01

    This book analyses, in an international comparative context, Portugal´s energy transition from organic sources to fossil fuels in the period 1856-2006. It investigates the role that energy played in the industrialization of the country and how the relationship between energy and economic growth changed with the transition from an industrial to a service society. A unique dataset of energy quantities and prices reveals that Portugal´s transition to fossil fuels and high-energy quantities wa...

  3. Spin-dependent structural, electronic and transport properties of armchair graphyne nanoribbons doped with single transition-metal atom, using DFT calculations

    Science.gov (United States)

    Golafrooz Shahri, S.; Roknabadi, M. R.; Radfar, R.

    2017-12-01

    In this present paper, the non-equilibrium Green function (NEGF) method along with the density functional theory (DFT) were used to investigate the effect of doping a single transition-metal atom on transport and electronic properties of armchair graphyne (γ-graphyne) nanoribbons. It can be deduced from the results that among the doped TM atoms, Mn and Fe cause stronger polarized currents comparing to Co and Ni. Mn-AGyNR represents the features of a half-semiconductor and behaves like a semiconductor in both up and down spin channels. On the other hand, Fe-AGyNR shows a great potential in spintronic applications due to its half-metal properties. Also our results show the promising application of armchair graphyne nanoribbons in nano-electrical devices.

  4. Topological band-order transition and quantum spin Hall edge engineering in functionalized X-Bi(111) (X = Ga, In, and Tl) bilayer

    Science.gov (United States)

    Kim, Youngjae; Yun, Won Seok; Lee, J. D.

    2016-09-01

    Functionalized X-Bi bilayers (X = Ga, In, and Tl) with halogens bonded on their both sides have been recently claimed to be the giant topological insulators due to the strong band inversion strengths. Employing the first-principles electronic structure calculation, we find the topological band order transition from the order p - p - s of the X-Bi bilayers with halogens on their both sides to the new order p - s - p of the bilayers (especially for X = Ga and In) with halogen on one side and hydrogen on the other side, where the asymmetric hydrogen bonding simulates the substrate. We further find that the p - s bulk band gap of the bilayer bearing the new order p - s - p sensitively depends on the electric field, which enables a meaningful engineering of the quantum spin Hall edge state by controlling the external electric field.

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

    Science.gov (United States)

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

    2016-03-07

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

  6. The Changing Outplacement Process. New Methods and Opportunities for Transition Management.

    Science.gov (United States)

    Meyer, John L.; Shadle, Carolyn C.

    This book, which is designed for consumers and providers of outplacement services, explores recent changes that have led to an essentially new type of service termed OTR (an acronym that stands for "outplacement, transition, relocation" when focusing on employees and for "outplacement, transition, and restructuring" when…

  7. Nucleic Acid-Dependent Conformational Changes in CRISPR-Cas9 Revealed by Site-Directed Spin Labeling.

    Science.gov (United States)

    Vazquez Reyes, Carolina; Tangprasertchai, Narin S; Yogesha, S D; Nguyen, Richard H; Zhang, Xiaojun; Rajan, Rakhi; Qin, Peter Z

    2017-06-01

    In a type II clustered regularly interspaced short palindromic repeats (CRISPR) system, RNAs that are encoded at the CRISPR locus complex with the CRISPR-associated (Cas) protein Cas9 to form an RNA-guided nuclease that cleaves double-stranded DNAs at specific sites. In recent years, the CRISPR-Cas9 system has been successfully adapted for genome engineering in a wide range of organisms. Studies have indicated that a series of conformational changes in Cas9, coordinated by the RNA and the target DNA, direct the protein into its active conformation, yet details on these conformational changes, as well as their roles in the mechanism of function of Cas9, remain to be elucidated. Here, nucleic acid-dependent conformational changes in Streptococcus pyogenes Cas9 (SpyCas9) were investigated using the method of site-directed spin labeling (SDSL). Single nitroxide spin labels were attached, one at a time, at one of the two native cysteine residues (Cys80 and Cys574) of SpyCas9, and the spin-labeled proteins were shown to maintain their function. X-band continuous-wave electron paramagnetic resonance spectra of the nitroxide attached at Cys80 revealed conformational changes of SpyCas9 that are consistent with a large-scale domain re-arrangement upon binding to its RNA partner. The results demonstrate the use of SDSL to monitor conformational changes in CRISPR-Cas9, which will provide key information for understanding the mechanism of CRISPR function.

  8. Morphological and acrosomal changes of canine spermatozoa during epididymal transit

    Science.gov (United States)

    2013-01-01

    Background During epididymal transit, functional and structural modifications leading to full maturation enable male gametes to reach, recognize and fertilize the oocytes. In dogs, little is known on the modifications of spermatozoa during the passage in the epididymis. The aim of this study was to describe the motility, morphology and acrosomal patterns of canine spermatozoa retrieved from the epididymis caput, corpus and cauda. Results After the dilution required for the collection of epididymal content, sperm motility was significantly higher (P orchiectomy for medical purposes. Further investigations should be also focused on the potential use of spermatozoa recovered from other epididymal regions. PMID:23442223

  9. Investigation of possible phase transition of the frustrated spin-1/2 J 1-J 2-J 3 model on the square lattice.

    Science.gov (United States)

    Hu, Ai-Yuan; Wang, Huai-Yu

    2017-09-05

    The frustrated spin-1/2 J 1-J 2-J 3 antiferromagnet with exchange anisotropy on the two-dimensional square lattice is investigated. The exchange anisotropy is presented by η with 0 ≤ η J 1, J 2, J 3 and anisotropy on the possible phase transition of the Néel state and collinear state are studied comprehensively. Our results indicate that for J 3 > 0 there are upper limits [Formula: see text] and η c values. When 0 J 3 ≤ [Formula: see text] and 0 ≤ η ≤ η c , the Néel and collinear states have the same order-disorder transition point at J 2 = J 1/2. Nevertheless, when the J 3 and η values beyond the upper limits, it is a paramagnetic phase at J 2 = J 1/2. For J 3 J 2 = J 1/2. Therefore, for J 2 = J 1/2, under such parameters, a first-order phase transition between the two states for these two cases below the critical temperatures may occur. When J 2 ≠ J 1/2, the Néel and collinear states may also exist, while they have different critical temperatures. When J 2 > J 1/2, a first-order phase transition between the two states may also occur. However, for J 2 J 1/2, the Néel state is always more stable than the collinear state.

  10. Hysteresis in the spin transition regime of [Fe(NH{sub 2}trz){sub 3}](NO{sub 3}){sub 2} as probed by ZF-{mu}SR

    Energy Technology Data Exchange (ETDEWEB)

    Ksenofontov, V. [Institut fuer Anorganische Chemie und Analytische Chemie, Universitaet Mainz, Staudingerweg 9, 55099 Mainz (Germany); Garcia, Y. [Unite de Chimie des Materiaux Inorganiques et Organiques, Departement de Chimie, Faculte des Sciences, Universite catholique de Louvain, Place Louis Pasteur 1, 1348 Louvain-la-Neuve (Belgium)]. E-mail: garcia@chim.ucl.ac.be; Campbell, S.J. [School of Physical, Environmental and Mathematical Sciences, The University of New South Wales, Australian Defence Force Academy, Canberra, ACT 2600 (Australia); Boland, Y. [Unite de Chimie des Materiaux Inorganiques et Organiques, Departement de Chimie, Faculte des Sciences, Universite catholique de Louvain, Place Louis Pasteur 1, 1348 Louvain-la-Neuve (Belgium); Lord, J.S. [ISIS, Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX (United Kingdom); Guetlich, P. [Institut fuer Anorganische Chemie und Analytische Chemie, Universitaet Mainz, Staudingerweg 9, 55099 Mainz (Germany)

    2006-03-31

    The thermal spin transition which occurs in the polymeric chain compound [Fe(NH{sub 2}trz){sub 3}](NO{sub 3}){sub 2} above room temperature has been investigated by zero-field muon spin relaxation ({mu}SR) ({approx}8-402K). The depolarization curves are best described by a Lorentzian and a Gaussian line that represent fast and slow components respectively. The spin transition is associated with a hysteresis loop of width {delta}T=34K (T{sub 1/2}{sup {up_arrow}}=346K and T{sub 1/2}{sup {down_arrow}}=312K) that has been delineated by the temperature variation of the initial asymmetry parameter. Comparison of zero-field and transverse field (20Oe) {mu}SR measurements shows that diamagnetic muon species occur over the entire temperature range, a large fraction of muons being however paramagnetic.

  11. Estimating the spin diffusion length and the spin Hall angle from spin pumping induced inverse spin Hall voltages

    Science.gov (United States)

    Roy, Kuntal

    2017-11-01

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

  12. Carbon cycle changes during the Triassic-Jurassic transition

    NARCIS (Netherlands)

    Ruhl, M.|info:eu-repo/dai/nl/304838357

    2010-01-01

    The end-Triassic is regarded as one of the five major mass extinction events of the Phanerozoic. This time interval is marked by up to 50% of marine biodiversity loss and major changes in terrestrial ecosystems. Mass extinction events are often marked by changes in the global carbon cycle. The

  13. Morphological and acrosomal changes of canine spermatozoa during epididymal transit.

    Science.gov (United States)

    Varesi, Sara; Vernocchi, Valentina; Faustini, Massimo; Luvoni, Gaia Cecilia

    2013-02-26

    During epididymal transit, functional and structural modifications leading to full maturation enable male gametes to reach, recognize and fertilize the oocytes. In dogs, little is known on the modifications of spermatozoa during the passage in the epididymis. The aim of this study was to describe the motility, morphology and acrosomal patterns of canine spermatozoa retrieved from the epididymis caput, corpus and cauda. After the dilution required for the collection of epididymal content, sperm motility was significantly higher (Pepididymal regions. A significantly increased prevalence of tail defects, mainly represented by single bent tails, was observed in the corpus compared to caput (Psperm with cytoplasmic droplets decreased from the proximal to the distal region of the epididymis. Particularly, proximal cytoplasmic droplets were more frequently found in spermatozoa collected from the caput epididymis than in the corpus (Pepididymal regions.

  14. Martensite-like transition and spin-glass behavior in nanocrystalline Pr0.5Ca0.5MnO3

    Directory of Open Access Journals (Sweden)

    S. Narayana Jammalamadaka

    2011-12-01

    Full Text Available We report on isothermal pulsed (20 ms field magnetization, temperature dependent AC – susceptibility, and the static low magnetic field measurements carried out on 10 nm sized Pr0.5Ca0.5MnO3 nanoparticles (PCMO10. The saturation field for the magnetization of PCMO10 (∼ 250 kOe is found to be reduced in comparison with that of bulk PCMO (∼300 kOe. With increasing temperature, the critical magnetic field required to ‘melt’ the residual charge-ordered phase decays exponentially while the field transition range broadens, which is indicative of a Martensite-like transition. The AC - susceptibility data indicate the presence of a frequency-dependent freezing temperature, satisfying the conventional Vogel-Fulcher and power laws, pointing to the existence of a spin-glass-like disordered magnetic phase. The present results lead to a better understanding of manganite physics and might prove helpful for practical applications.

  15. Some recent developments in spin glasses

    Indian Academy of Sciences (India)

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

  16. Some recent developments in spin glasses

    Indian Academy of Sciences (India)

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

  17. Tuning size and thermal hysteresis in bistable spin crossover nanoparticles.

    Science.gov (United States)

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

    2010-06-21

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

  18. Rotation Rates and Spin Changes of Jupiter Family Comet Nuclei: New optical lightcurves and an update on the population properties.

    Science.gov (United States)

    Kokotanekova, Rosita; Snodgrass, Colin; Lacerda, Pedro; Green, Simon F.

    2016-10-01

    In this work, we revise the physical characteristics of Jupiter family comets (JFCs) by expanding the sample of nuclei with known rotational and shape properties.The study provides a review of the properties of all JFCs with known rotation rates derived from optical, radar or spacecraft measurements. This sample is complemented by newly obtained lightcurves of eight comets which are used to improve the precision of some known spin rates as well as to add new objects to the sample. We derive the new lightcurves from archival data partially taken within the framework of the Survey of Ensemble Physical Properties of Cometary Nuclei (SEPPCoN) and from devoted phase function observing campaigns. The lightcurves are produced with a specially-developed pipeline which enables data from various instruments at different epochs and geometries to be analyzed together. All lightcurves are absolutely calibrated using PanSTARRs photometric standards. Combining photometric measurements from different epochs allows us to achieve high precision in the period determinations and to constrain the phase functions of the comets. For three of the comets - 8P/Tuttle, 110P/Hartley 3 and 162P/Siding Spring - we obtain well-sampled phase functions which we compare to these of other well-studied JFCs.The newly added data provide us with a better-constrained sample which we use to compare JFC characteristics with the rotation rates, shapes and surface properties of other small-body populations.A special focus is put on the handful of JFCs which are known to demonstrate spin changes on orbital timescales. We are expanding this sample by adding new lightcurves derived from archival data as well as from our targeted survey using 2-4m telescopes. The rotational changes are obtained by comparison of the comets' current spin rates to those from previous apparitions. Using the new extended sample, we study the relation between the measured period changes and the physical properties of the nuclei.

  19. Post-Newtonian templates for binary black-hole inspirals: the effect of the horizon fluxes and the secular change in the black-hole masses and spins

    Science.gov (United States)

    Isoyama, Soichiro; Nakano, Hiroyuki

    2018-01-01

    Black holes (BHs) in an inspiraling compact binary system absorb the gravitational-wave (GW) energy and angular-momentum fluxes across their event horizons and this leads to the secular change in their masses and spins during the inspiral phase. The goal of this paper is to present ready-to-use, 3.5 post-Newtonian (PN) template families for spinning, non-precessing, binary BH inspirals in quasicircular orbits, including the 2.5 PN and 3.5 PN horizon-flux contributions as well as the correction due to the secular change in the BH masses and spins through 3.5 PN order, respectively, in phase. We show that, for binary BHs observable by Advanced LIGO with high mass ratios (larger than  ∼10) and large aligned-spins (larger than  ∼ 0.7 ), the mismatch between the frequency-domain template with and without the horizon-flux contribution is typically above the 3% mark. For (supermassive) binary BHs observed by LISA, even a moderate mass-ratios and spins can produce a similar level of the mismatch. Meanwhile, the mismatch due to the secular time variations of the BH masses and spins is well below the 1% mark in both cases, hence this is truly negligible. We also point out that neglecting the cubic-in-spin, point-particle phase term at 3.5 PN order would deteriorate the effect of BH absorption in the template.

  20. Dependence of nuclear quadrupole resonance transitions on the electric field gradient asymmetry parameter for nuclides with half-integer spins

    Science.gov (United States)

    Cho, Herman

    2016-09-01

    Allowed transition energies and eigenstate expansions have been calculated and tabulated in numerical form as functions of the electric field gradient asymmetry parameter for the zero field Hamiltonian of quadrupolar nuclides with I = 3 / 2 , 5 / 2 , 7 / 2, and 9 / 2. These results are essential to interpret nuclear quadrupole resonance (NQR) spectra and extract accurate values of the electric field gradient tensors. Applications of NQR methods to studies of electronic structure in heavy element systems are proposed.

  1. Stages of Change or Changes of Stage? Predicting Transitions in Transtheoretical Model Stages in Relation to Healthy Food Choice

    Science.gov (United States)

    Armitage, Christopher J.; Sheeran, Paschal; Conner, Mark; Arden, Madelynne A.

    2004-01-01

    Relatively little research has examined factors that account for transitions between transtheoretical model (TTM) stages of change. The present study (N=787) used sociodemographic, TTM, and theory of planned behavior (TPB) variables, as well as theory-driven interventions to predict changes in stage. Longitudinal analyses revealed that…

  2. Ferromagnetism at Room Temperature Induced by Spin Structure Change in BiFe1-x Cox O3 Thin Films.

    Science.gov (United States)

    Hojo, Hajime; Kawabe, Ryo; Shimizu, Keisuke; Yamamoto, Hajime; Mibu, Ko; Samanta, Kartik; Saha-Dasgupta, Tanusri; Azuma, Masaki

    2017-03-01

    The coexistence and coupling of ferromagnetic and ferroelectric orders in a single material is crucial for realizing next-generation multifunctional applications. The coexistence of such orders is confirmed at room temperature in epitaxial thin films of BiFe1-x Cox O3 (x ≤ 0.15), which manifests a spin structure change from a low-temperature cycloidal one to a high-temperature collinear one with canted ferromagnetism. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Transitional states in marine fisheries: adapting to predicted global change

    Science.gov (United States)

    MacNeil, M. Aaron; Graham, Nicholas A. J.; Cinner, Joshua E.; Dulvy, Nicholas K.; Loring, Philip A.; Jennings, Simon; Polunin, Nicholas V. C.; Fisk, Aaron T.; McClanahan, Tim R.

    2010-01-01

    Global climate change has the potential to substantially alter the production and community structure of marine fisheries and modify the ongoing impacts of fishing. Fish community composition is already changing in some tropical, temperate and polar ecosystems, where local combinations of warming trends and higher environmental variation anticipate the changes likely to occur more widely over coming decades. Using case studies from the Western Indian Ocean, the North Sea and the Bering Sea, we contextualize the direct and indirect effects of climate change on production and biodiversity and, in turn, on the social and economic aspects of marine fisheries. Climate warming is expected to lead to (i) yield and species losses in tropical reef fisheries, driven primarily by habitat loss; (ii) community turnover in temperate fisheries, owing to the arrival and increasing dominance of warm-water species as well as the reduced dominance and departure of cold-water species; and (iii) increased diversity and yield in Arctic fisheries, arising from invasions of southern species and increased primary production resulting from ice-free summer conditions. How societies deal with such changes will depend largely on their capacity to adapt—to plan and implement effective responses to change—a process heavily influenced by social, economic, political and cultural conditions. PMID:20980322

  4. Antiferromagnetic spin Seebeck effect.

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-03-03

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

  5. Antiferromagnetic Spin Seebeck Effect.

    Science.gov (United States)

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

    2016-03-04

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

  6. Co K-edge magnetic circular dichroism across the spin state transition in LaCoO3 single crystal

    Science.gov (United States)

    Efimov, V.; Ignatov, A.; Troyanchuk, I. O.; Sikolenko, V. V.; Rogalev, A.; Wilhelm, F.; Efimova, E.; Tiutiunnikov, S. I.; Karpinsky, D.; Kriventsov, V.; Yakimchuk, E.; Molodtsov, S.; Sainctavit, P.; Prabhakaran, D.

    2016-05-01

    We report on Co K-edge x-ray magnetic circular dichroism (XMCD) measurements of LaCoO3 single crystal in temperature range from 5 to 300 K and external magnetic field of 17 T. The response consists of pre-edge (at 7712 eV) and bi-polar peak (up at 7727, down at 7731 eV) with amplitudes, respectively, less than 10-3 and 10-2 of the Co K-edge jump. Using the sum rule the orbital magnetic moment of 4p Co is evaluated. Its temperature dependence reaches a maximum of (2.7 ± 0.9) x10-3 μB at 120 K, following the trend for the total magnetic moment on the Co obtained from the superconducting quantum interference device measurements. However, on warming from 25 to 120 K, the orbital magnetic moment of the 4p Co doubles while total magnetic moment of Co increases 10 times. First principle calculations are in order to relate the Co K-edge XMCD results to the orbital and spin moment of 3d Co.

  7. First-order transition on the frustrated spin-1/2 Heisenberg ferromagnet on an anisotropic square lattice

    Energy Technology Data Exchange (ETDEWEB)

    Lapa, Rodrigo S.; Mendonça, Griffith [Departamento de Fi' sica, Universidade Federal de Minas Gerais, CP 702, 30161-970 Belo Horizonte, MG (Brazil); Universidade Federal do Amazonas, Departamento de Fi' sica, 3000, Japiim, 69077-000 Manaus, AM (Brazil); Roberto Viana, J. [Universidade Federal do Amazonas, Departamento de Fi' sica, 3000, Japiim, 69077-000 Manaus, AM (Brazil); Ricardo de Sousa, J., E-mail: jsousa@ufam.edu.br [Universidade Federal do Amazonas, Departamento de Fi' sica, 3000, Japiim, 69077-000 Manaus, AM (Brazil); National Institute of Science and Technology for Complex Systems, Universidade Federal do Amazonas, Departamento de Fisica, 3000, Japiim, 69077-000 Manaus, AM (Brazil)

    2014-11-15

    We have studied the quantum spin-1/2 frustrated Heisenberg model with two ferromagnetic interactions: nearest-neighbor (NN) with different coupling strengths J{sub 1} and J{sub 1}{sup ′} along x and y directions, respectively, competing with a next-nearest-neighbor (NNN) with coupling J{sub 2}. Using the effective-field theory we obtain the ground-state phase diagram in the (λ,α) space, where λ=J{sub 1}{sup ′}/J{sub 1} and α=J{sub 2}/J{sub 1}. Depending on the values of λ and α we observe three different states: ferromagnetic (F), collinear ferromagnetic (CF) and quantum paramagnetic (QP). We observe a QP state between the ordered F and CF phases in the region λ{sub 1}<λ<1 (λ{sub 1}≃0.62). - Highlights: • We study the ferromagnetic J{sub 1}−J{sub 1}{sup ′}−J{sub 2} model on an anisotropic square lattice by using effective-field theory. • We obtain the ground phase diagram in the λ−α plane (λ=J{sub 1}{sup ′}/J{sub 1} and α=J{sub 2}/J{sub 1}). • A comparison with the results of the antiferromagnetic J{sub 1}−J{sub 1}{sup ′}−J{sub 2} model. • We propose a functional for the free energy.

  8. Protective spin-labeled fluorenes maintain amyloid beta peptide in small oligomers and limit transitions in secondary structure

    Energy Technology Data Exchange (ETDEWEB)

    Altman, Robin [Univ. of California, Davis, CA (United States). Dept. of Biochemistry and Molecular Medicine; Ly, Sonny [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Physical and Life Science Directorate; Hilt, Silvia [Univ. of California, Davis, CA (United States). Dept. of Biochemistry and Molecular Medicine; Petrlova, Jitka [Univ. of California, Davis, CA (United States). Dept. of Biochemistry and Molecular Medicine; Maezawa, Izumi [Univ. of California Davis, Sacramento, CA (United States). MIND Inst. and Dept. of Pathology and Laboratory Medicine; Kálai, Tamás [Univ. of Pecs (Hungary). Inst. of Organic and Medicinal Chemistry; Hideg, Kálmán [Univ. of Pecs (Hungary). Inst. of Organic and Medicinal Chemistry; Jin, Lee-Way [Univ. of California Davis, Sacramento, CA (United States). MIND Inst. and Dept. of Pathology and Laboratory Medicine; Laurence, Ted A. [Univ. of California, Davis, CA (United States). Dept. of Biochemistry and Molecular Medicine; Voss, John C. [Univ. of California, Davis, CA (United States). Dept. of Biochemistry and Molecular Medicine

    2015-12-01

    Alzheimer’s disease is characterized by the presence of extracellular plaques comprised of amyloid beta (Aβ) peptides. Soluble oligomers of the Aβ peptide underlie a cascade of neuronal loss and dysfunction associated with Alzheimer's disease. Single particle analyses of Aβ oligomers in solution by fluorescence correlation spectroscopy (FCS) were used to provide real-time descriptions of how spin-labeled fluorenes (SLFs; bi-functional small molecules that block the toxicity of Aβ) prevent and disrupt oligomeric assemblies of Aβ in solution. The FCS results, combined with electron paramagnetic resonance spectroscopy and circular dichroism spectroscopy, demonstrate SLFs can inhibit the growth of Aβ oligomers and disrupt existing oligomers while retaining Aβ in a largely disordered state. Furthermore, while the ability of SLF to block Aβ toxicity correlates with a reduction in oligomer size, our results suggest the conformation of Aβ within the oligomer determines the toxicity of the species. Attenuation of Aβ toxicity, which has been associated primarily with the soluble oligomeric form, can be achieved through redistribution of the peptides into smaller oligomers and arrest of the fractional increase in beta secondary structure.

  9. Spectroscopic signature of the superparamagnetic transition and surface spin disorder in CoFe2O4 nanoparticles.

    Science.gov (United States)

    Sun, Qi-C; Birkel, Christina S; Cao, Jinbo; Tremel, Wolfgang; Musfeldt, Janice L

    2012-06-26

    Phonons are exquisitely sensitive to finite length scale effects in a wide variety of materials. To investigate confinement in combination with strong magnetoelastic interactions, we measured the infrared vibrational properties of CoFe(2)O(4) nanoparticles and compared our results to trends in the coercivity over the same size range and to the response of the bulk material. Remarkably, the spectroscopic response is sensitive to the size-induced crossover to the superparamagnetic state, which occurs between 7 and 10 nm. A spin-phonon coupling analysis supports the core-shell model. Moreover, it provides an estimate of the magnetically disordered shell thickness, which increases from 0.4 nm in the 14 nm particles to 0.8 nm in the 5 nm particles, demonstrating that the associated local lattice distortions take place on the length scale of the unit cell. These findings are important for understanding finite length scale effects in this and other magnetic oxides where magnetoelastic interactions are important.

  10. A Case Study of Leadership Transition: Continuity and Change

    Science.gov (United States)

    Cocklin, Barry; Wilkinson, Jane

    2011-01-01

    Few studies of school leadership succession document the processes of continuity and change, especially within situations where there has been a strong tradition of tenure of principal, within a "quality" school. This article examines how a new principal with a commitment towards notions of Learning Community Schools, "quality" teaching and…

  11. Rural healthcare in transition. A time for change management.

    Science.gov (United States)

    Hart, J P

    1988-09-01

    The fundamental challenge for rural healthcare leaders today is to address three key questions: What is the nature of the system that is undergoing change? What are the nature and extent of the changes? What strategies are needed to manage in a climate of change? Healthcare administrators' perspective of rural healthcare systems must take into account the full range of provider organizations, promote the idea of continuum of care, and consider system and environment as mutually dependent parts of a larger whole. The environments that have influenced rural healthcare delivery and organization in the 1980s include demographics, epidemiology, economics, finances, personnel, technology, regulations, and politics. As hospital admissions and patient days declined under the pressures of cost containment, population shifts, and changes in medical practice, rural hospitals sought to maintain viability through a variety of adaptive actions, such as downsizing, forming relationships with other hospitals, and diversifying. These environmental and restructuring trends will require some degree of adaptation by rural healthcare organizations. Leaders will have to shift the organization toward a horizontal orientation, which emphasizes participation by department heads and supervisors in defining and implementing interorganizational relationships; authority for horizontal action taking and seeking out additional connections that will improve continuity and quality of care; and team-building skills to enhance cooperation and effectiveness.

  12. Dependence of nuclear quadrupole resonance transitions on the electric field gradient asymmetry parameter for nuclides with half-integer spins

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Herman

    2016-09-01

    Allowed transition energies and eigenstate expansions have been calculated and tabulated in numerical form as functions of the electric field gradient asymmetry parameter for the zero field Hamiltonian of quadrupolar nuclides with I = 3/2, 5/2, 7/2, and 9/2. These results may be used to interpret nuclear quadrupole resonance (NQR) spectra and extract accurate values of the electric field gradient tensors. Applications of NQR methods to studies of electronic structure in heavy element systems are proposed. This material is based upon work supported by the U.S. Department of Energy Office of Science, Office of Basic Energy Sciences, Heavy Element Chemistry program.

  13. The zero-moment half metal: How could it change spin electronics?

    Directory of Open Access Journals (Sweden)

    Davide Betto

    2016-05-01

    Full Text Available The Heusler compound Mn2RuxGa (MRG may well be the first compensated half metal. Here, the structural, magnetic and transport properties of thin films of MRG are discussed. There is evidence of half-metallicity up to x = 0.7, and compensation of the two Mn sublattice moments is observed at specific compositions and temperatures, leading to a zero-moment half metal. There are potential benefits for using such films with perpendicular anisotropy for spin-torque magnetic tunnel junctions and oscillators, such as low critical current, high tunnel magnetoresistance ratio, insensitivity to external fields and resonance frequency in the THz range.

  14. The zero-moment half metal: How could it change spin electronics?

    Energy Technology Data Exchange (ETDEWEB)

    Betto, Davide; Rode, Karsten, E-mail: rodek@tcd.ie; Thiyagarajah, Naganivetha; Lau, Yong-Chang; Borisov, Kiril; Atcheson, Gwenael; Stamenov, Plamen; Coey, J. M. D. [CRANN, AMBER and School of Physics, Trinity College Dublin, Dublin 2 (Ireland); Žic, Mario; Archer, Thomas [CRANN, and School of Physics, Trinity College Dublin, Dublin 2 (Ireland)

    2016-05-15

    The Heusler compound Mn{sub 2}Ru{sub x}Ga (MRG) may well be the first compensated half metal. Here, the structural, magnetic and transport properties of thin films of MRG are discussed. There is evidence of half-metallicity up to x = 0.7, and compensation of the two Mn sublattice moments is observed at specific compositions and temperatures, leading to a zero-moment half metal. There are potential benefits for using such films with perpendicular anisotropy for spin-torque magnetic tunnel junctions and oscillators, such as low critical current, high tunnel magnetoresistance ratio, insensitivity to external fields and resonance frequency in the THz range.

  15. Changes in Service and Associated Ridership Impacts near a New Light Rail Transit Line

    Directory of Open Access Journals (Sweden)

    Jeongwoo Lee

    2017-10-01

    Full Text Available Los Angeles (LA, for many years a city with limited rail transit, is substantially expanding its public transit system. This paradigm change in transportation policy and investment creates new requirements for monitoring. One area needing evaluation is whether new, high quality transit options, such as light rail, near existing transit services increase sustainable transportation mode shares and reduce car travel. Few studies have explored light rail’s role as a catalyst to increase overall transit use and achieve sustainability goals within an auto-oriented city like LA. Metro’s data show that trips taken on its bus and rail system dropped overall by 10.5% between 2009 and 2016, but its rail ridership grew 21% during the same period due to the debut of the Gold Line and Expo Line extensions. We analyze changes to bus service and associated ridership impacts that resulted from the opening of these two LRT lines in LA. The immediate effect of the city’s bus service changes along the Gold Line light rail extension appear to be associated with a net “bus plus rail” ridership decline in that corridor. In contrast, the Expo Line corridor experienced an initial increase in ridership during the two years immediately after its opening, possibly because the bus service was not reduced by the same magnitude as along the Gold Line extension. Our findings indicate that changes in bus service made to coincide with the introduction of new light rail transit (LRT can negatively affect the overall transit ridership in the corridor. Planners and policy makers should closely monitor changes in bus service and ridership associated with new rail transit to ensure investments results in an overall net increase in more sustainable travel.

  16. Quantum spin transistor with a Heisenberg spin chain

    Science.gov (United States)

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

    2016-01-01

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

  17. Policies for system change: the transition to the bioeconomy

    DEFF Research Database (Denmark)

    Scordato, Lisa; Bugge, Markus M.; Hansen, Teis

    Over the past 10-15 years the bioeconomy has increased in importance and has been promoted as a possible contribution to address important societal challenges such as climate change, food security, and global health issues. It is argued that the development towards a circular bioeconomy can...... policies are in fact giving sufficient importance to transformative failures (vis-à-vis market and structural failures). Also, to the extent that transformative failures are given attention in bioeconomy policies, we don’t know whether this is consistent in the policy mix or only in terms of formulating...

  18. Political economy and price ratio changes: Electric industry under transition

    Science.gov (United States)

    Reidy, Mary E.

    This study began early in 2000, when the electric market was beginning to evolve from a vertical integrated industry to a market-driven, global industry where the generation portion of the industry was being sold to independent market-based companies. The beginnings of acquisitions, restructuring and re-alignments of the transmission and distribution systems were heightened during this period. In addition, as this study was underway, a tumultuous restructuring in California caused some proponents of deregulation to question the changes. The purpose of this study is to investigate price changes at the state level during the last 10 years (1990-2000). The conceptual framework is built on a study released in 1996. This study predicted lower prices as deregulation in the electric industry occurred and consumers had more choices in suppliers. In order to gain additional insight, the study is comprised of a quantitative analysis of price changes over time as well as a qualitative investigation of a certain geographic area. As a result of the quantitative analysis performed, the study has failed to reject the null hypothesis that deregulated states exhibited no difference in price ratios than those states that remain regulated. This was tested at the level of political influence (states with elected versus appointed) commissions. In fact, whether the population is segmented nationally, regionally, politically or by level of deregulation, price ratios have decreased from 1985-1996. National price ratios have been declining since the mid-1980s. A flattening of the trend for the last four years (1997-2000) may be due to the current retrenching as a result of the California deregulation experience. The qualitative section seeks to understand what influences electric prices have on regional economic development efforts. The interview results have determined that lower electric prices help to contribute to successful economic development activities, but they are not the

  19. Microelectromechanical systems integrating molecular spin crossover actuators

    Energy Technology Data Exchange (ETDEWEB)

    Manrique-Juarez, Maria D. [LCC, CNRS and Université de Toulouse, UPS, INP, F-31077 Toulouse (France); LAAS, CNRS and Université de Toulouse, INSA, UPS, F-31077 Toulouse (France); Rat, Sylvain; Salmon, Lionel; Molnár, Gábor; Bousseksou, Azzedine, E-mail: liviu.nicu@laas.fr, E-mail: azzedine.bousseksou@lcc-toulouse.fr [LCC, CNRS and Université de Toulouse, UPS, INP, F-31077 Toulouse (France); Mathieu, Fabrice; Saya, Daisuke; Séguy, Isabelle; Leïchlé, Thierry; Nicu, Liviu, E-mail: liviu.nicu@laas.fr, E-mail: azzedine.bousseksou@lcc-toulouse.fr [LAAS, CNRS and Université de Toulouse, INSA, UPS, F-31077 Toulouse (France)

    2016-08-08

    Silicon MEMS cantilevers coated with a 200 nm thin layer of the molecular spin crossover complex [Fe(H{sub 2}B(pz){sub 2}){sub 2}(phen)] (H{sub 2}B(pz){sub 2} = dihydrobis(pyrazolyl)borate and phen = 1,10-phenantroline) were actuated using an external magnetic field and their resonance frequency was tracked by means of integrated piezoresistive detection. The light-induced spin-state switching of the molecules from the ground low spin to the metastable high spin state at 10 K led to a well-reproducible shift of the cantilever's resonance frequency (Δf{sub r} = −0.52 Hz). Control experiments at different temperatures using coated as well as uncoated devices along with simple calculations support the assignment of this effect to the spin transition. This latter translates into changes in mechanical behavior of the cantilever due to the strong spin-state/lattice coupling. A guideline for the optimization of device parameters is proposed so as to efficiently harness molecular scale movements for large-scale mechanical work, thus paving the road for nanoelectromechanical systems (NEMS) actuators based on molecular materials.

  20. [Changes in factors associated with the nutrition transition in Mexico].

    Science.gov (United States)

    Ortiz-Hernández, Luis; Delgado-Sánchez, Guadalupe; Hernández-Briones, Ana

    2006-01-01

    To describe the demographic and socioeconomic changes, food availability and food expense in Mexico during 1980-2000. From official statistics (Population Census, FAO Food Balance Sheets, Family Income and Expense National Survey and Economic Census) we estimated the evolution of population distribution according to locality size, occupational structure, woman participation in the wage-earning labor force, minimum wage, availability of food establishments and expense in food. The percentage of the population that lives in urban areas has increased, they are employed in the tertiary sector, womens participation in the labor market has increased but real minimum wages have decreased. Vegetables, oleaginous, oils, fish and seafood availability have decreased whereas animal fat, vegetables, fruits, softdrinks, meats and egg availability have increased. The number of inexpensive restaurants (cocinas económicas and fondas) has also increased. Food expenses have decreased while amount of money spent in food consumed away from home has increased. In Mexico, the growth in urban areas and the tertiary job sector shows a parallel growth in the availability of high fat and protein food, a greater diet variety and more opportunities to consume food not prepared in the home. On the other hand, the sale of equipment and places designed for recreational physical activity have increased. By reducing employment in the primary sector it is foreseeable that labor intensive physical activity will become less important overtime.

  1. Gendering democratisation: women as change agents in transition contexts

    Directory of Open Access Journals (Sweden)

    Andrea Fleschenberg Fleschenberg

    2012-02-01

    Full Text Available During the last two decades, women politicians have emerged as female democratisation agents, i.e. change agents who actively lobby, struggle and organize for a pro-democracy regime change and a subsequent functioning democratic system, often with a (or the only mass following – whose personal sacrifices, political contributions and legacies arelargely overlooked or contested in related democratisation and gender studies. This article aims to critically assess in how far democratisation and gender studies have systematically studied and analysed the contributions towards democratisation and the consolidation of democracy made by women as head of state or government. It is argued, that there is a strong research desideratum with regard to this phenomenon despite statistical evidence in Latin America, Europe, sub-Saharan Africa and Asia. An overview of different case studies of women heads of state and government in Southern and Eastern Europe, Latin America, South and Southeast Asia is presented, outlining the career paths, political agenda and democratisation record of the respective female democratisation agents. Nevertheless, systematic and substantial research needs to be conducted to allow a profound and appropriate assessment of the political performance and legacies of female democratisation agents at the top echelons of political power. These studies can contribute to a better understanding of the nexus of gender and democratisation, gender and politics as well as to enlarge the explanatory strength of democratisation theories in general.Durante las dos últimas décadas, las mujeres políticas han emergido como agentes femeninos de democratización, es decir agentes de cambio como grupos de presión activos, que luchan y se organizan en pro de un cambio hacia el régimen democrático y al subsiguiente funcionamiento del sistema, a menudo con el seguimiento de las masas (incluso el único – quienes con sus sacrificios

  2. A mean field study of quantum transitions in a spin-1/2 XY chain with a transverse long-range interaction

    Science.gov (United States)

    Sousa, H. S.; de Lima, J. P.; Costa, N. C.; Lyra, M. L.; Gonçalves, L. L.

    2017-11-01

    We study the anisotropic one-dimensional XY model (s = 1/2 ) with uniform long-range interaction between the transverse components of the spins. The solution of the model was obtained by using the Jordan-Wigner transformation, and by treating the four fermion term within the mean field approximation. The proposed approximation reproduces the known exact results for two limiting cases of the model, namely, the isotropic model with long-range interaction and the anisotropic model without long-range interaction. Explicit expressions are obtained for the Helmholtz free energy, the induced magnetization and the isothermal susceptibility at arbitrary temperatures. Special attention is given to the study of quantum critical behaviour at T = 0 , by determining the phase diagram for the quantum phase transitions, and it is shown that the system presents a critical behaviour analogous to the one presented by isotropic model with long-range interaction. The spontaneous magnetization is also determined, at T = 0 , and we show that our results obtained by mean field approximation are in good agreement with those obtained by exact diagonalization of a finite chain; a comparison is also made with already known results.

  3. Transition-Metal Pentatelluride ZrTe_{5} and HfTe_{5}: A Paradigm for Large-Gap Quantum Spin Hall Insulators

    Directory of Open Access Journals (Sweden)

    Hongming Weng

    2014-01-01

    Full Text Available Quantum spin Hall (QSH insulators, a new class of quantum matter, can support topologically protected helical edge modes inside a bulk insulating gap, which can lead to dissipationless transport. A major obstacle to reaching a wide application of QSH is the lack of suitable QSH compounds, which should be easily fabricated and have a large bulk gap. Here, we predict that single-layer ZrTe_{5} and HfTe_{5} are the most promising candidates for large-gap insulators, with a bulk direct (indirect band gap as large as 0.4 eV (0.1 eV and which are robust against external strains. The three-dimensional crystals of these two materials are good layered compounds with very weak interlayer bonding, and they are located near the phase boundary between weak and strong topological insulators, paving a new way for future experimental studies on both the QSH effect and topological phase transitions.

  4. Canted spin structure and the first order magnetic transition in CoFe{sub 2}O{sub 4} nanoparticles coated by amorphous silica

    Energy Technology Data Exchange (ETDEWEB)

    Lyubutin, I.S. [Shubnikov Institute of Crystallography, Russian Academy of Sciences, Moscow 119333 (Russian Federation); Starchikov, S.S., E-mail: sergey.s.starchikov@gmail.com [Shubnikov Institute of Crystallography, Russian Academy of Sciences, Moscow 119333 (Russian Federation); Gervits, N.E.; Korotkov, N.Yu.; Dmitrieva, T.V. [Shubnikov Institute of Crystallography, Russian Academy of Sciences, Moscow 119333 (Russian Federation); Lin, Chun-Rong, E-mail: crlinspin@gmail.com [Department of Applied Physics, National Pingtung University, Pingtung County 90003, Taiwan (China); Tseng, Yaw-Teng [Department of Applied Physics, National Pingtung University, Pingtung County 90003, Taiwan (China); Shih, Kun-Yauh [Department of Applied Chemistry, National Pingtung University, Pingtung County 90003, Taiwan (China); Lee, Jiann-Shing [Department of Applied Physics, National Pingtung University, Pingtung County 90003, Taiwan (China); Wang, Cheng-Chien [Department of Chemical and Materials Engineering, Southern Taiwan University of Science and Technology, Tainan 710, Taiwan (China)

    2016-10-01

    The functional polymer (PMA-co-MAA) latex microspheres were used as a core template to prepare magnetic hollow spheres consisting of CoFe{sub 2}O{sub 4}/SiO{sub 2} composites. The spinel type crystal structure of CoFe{sub 2}O{sub 4} ferrite is formed under annealing, whereas the polymer cores are completely removed after annealing at 450 °C. Magnetic and Mössbauer spectroscopy measurements reveal very interesting magnetic properties of the CoFe{sub 2}O{sub 4}/SiO{sub 2} hollow spheres strongly dependent on the particle size which can be tuned by the annealing temperature. In the ground state of low temperatures, the CoFe{sub 2}O{sub 4} nanoparticles are in antiferromagnetic state due to the canted magnetic structure. Under heating in the applied field, the magnetic structure gradually transforms from canted to collinear, which increases the magnetization. The Mössbauer data revealed that the small size CoFe{sub 2}O{sub 4}/SiO{sub 2} particles (2.2–4.3 nm) do not show superparamagnetic behavior but transit from the magnetic to the paramagnetic state by a jump-like magnetic transition of the first order This effect is a specific property of the magnetic nanoparticles isolated by inert material, and can be initiated by internal pressure creating at the particle surface. The suggested method of synthesis can be modified with various bio-ligands on the silane surface, and such materials can find many applications in diagnostics and bio-separation. - Highlights: • CoFe{sub 2}O{sub 4}/SiO{sub 2} nanocomposites in shell of hollow microcapsules designed for biomedical applications • The CoFe{sub 2}O{sub 4} particle size and magnetic properties can be tuned by thermal treatment • Canted spin structure in the CoFe{sub 2}O{sub 4} nanoparticles coated by SiO{sub 2} • The first order magnetic transition in the CoFe{sub 2}O{sub 4} nanoparticles coated by silica.

  5. Spin current

    CERN Document Server

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

    2012-01-01

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

  6. How does the spin-state of Co ions affect the insulator-metal transition in Bi2A2Co2O8 (A?=?Ca, Sr, Ba)?

    OpenAIRE

    Xiaokun Huang; Weiyi Zhang

    2016-01-01

    The misfit layered Bi2A2Co2O8 (A?=?Ca, Sr, Ba) compounds experience an insulator to metal transition as A?s ionic radius increases. This feature is contradictory to the conventional wisdom that larger lattice constant favors insulating rather than metallic state, and is also difficult to be reconciled using the Anderson weak localization theory. In this paper, we show from the first-principles calculation that an insulator-metal transition takes place from a nonmagnetic low-spin state of Co3+...

  7. Safety-collision transition induced by lane changing in traffic flow

    Science.gov (United States)

    Naito, Yuichi; Nagatani, Takashi

    2011-03-01

    We study the traffic behavior when a vehicle changes from the first lane to the second lane on a two-lane highway. We apply the optimal velocity model to the vehicular motion. If the incoming vehicle does not decelerate successfully, it crashes into the vehicle ahead. On the other hand, if the headway between the incoming vehicle and the vehicle behind on the second lane is not long sufficiently, the rear vehicle may come into collision with the incoming vehicle. The safety-collision transition occurs by changing the lane. The dynamical transition depends highly on the vehicular speed, the sensitivity, and the headway. We derive the phase diagram (or region map) for the safety-collision transition.

  8. Examining Change in Cortisol Patterns During the 10-week Transition to a New Childcare Setting

    Science.gov (United States)

    Bernard, Kristin; Peloso, Elizabeth; Laurenceau, Jean-Philippe; Zhang, Zhiyong; Dozier, Mary

    2014-01-01

    The transition to out-of-home childcare brings a number of challenges for children, including complex peer interactions and extended separations from parents. Children often show a midmorning-to-afternoon rise in cortisol on childcare days, compared to the typical diurnal decline seen at home. Changes in cortisol were examined in a wide age range of children (N = 168; 1.2mos–8yrs, M = 3.27yrs) during the 10-week transition to a new childcare setting. Structural equation modeling using latent change scores showed that children experienced an increase in the cortisol rise at childcare across the 10-week transition. Further, child age moderated the difference between home and childcare cortisol patterns. Findings are placed in a developmental context, and potential implications and future directions are discussed. PMID:25283439

  9. Youth Transitions, VET and the "Making" of Class: Changing Theorisations for Changing Times?

    Science.gov (United States)

    Avis, James; Atkins, Liz

    2017-01-01

    The paper places youth transitions and vocational education and training (VET) within the global policy context in which economic competiveness is hegemonic. It compares research from the 1970s/80s, which explored young peoples' lived experiences of VET and youth training schemes with contemporary work on similar themes. It argues that there are…

  10. Policy entrepreneurs and change strategies : Lessons from sixteen case studies of water transitions around the globe

    NARCIS (Netherlands)

    Meijerink, Sander; Huitema, Dave

    2010-01-01

    This paper focuses on the role of policy entrepreneurs in realizing water policy transitions. The central questions are to what extent have policy entrepreneurs played a role in realizing major change in water policies, who are these policy entrepreneurs, and what strategies have they used to bring

  11. Changes in Sleep Duration During Transition to Statutory Retirement: A Longitudinal Cohort Study.

    Science.gov (United States)

    Myllyntausta, Saana; Salo, Paula; Kronholm, Erkki; Aalto, Ville; Kivimäki, Mika; Vahtera, Jussi; Stenholm, Sari

    2017-07-01

    This study examined whether sleep duration changes during the transition from full-time work to statutory retirement and, if this were the case, which preretirement factors, including sociodemographic, work, lifestyle, and health factors, predict these changes. Data from repeated surveys of the Finnish Public Sector study, linked to records of retirement, were used. The study population consisted of 5785 participants who retired on a statutory basis in 2000-2011 and who had responded to surveys on sleep duration at least once immediately before and after their retirement (mean number of repeat study waves 3.6). Linear regression analyses with generalized estimating equations were used to examine changes in sleep duration around retirement. Before retirement there was a slight decrease in sleep duration. During the 4-year retirement transition, sleep duration increased from 7 hours 0 minutes (95% confidence interval [CI] 6 hours 54 minutes to 7 hours 6 minutes) to 7 hours and 22 minutes (95% CI 7 hours 16 minutes to 7 hours 27 minutes); thus, mean increase being 22 minutes. Increase in sleep duration was greatest in those who were short sleepers, heavy drinkers, or had sleep difficulties. After the retirement transition, sleep duration remained at approximately the same level, as no significant changes were observed. This longitudinal study suggests that transition from full-time work to statutory retirement is associated with an increase in sleep duration.

  12. Changes in Drinking Patterns across the Transition to College among First-Year College Males

    Science.gov (United States)

    LaBrie, Joseph; Lamb, Toby; Pedersen, Eric

    2009-01-01

    Few studies examine changes in drinking behavior during the transition from high school to college. Using a sample of 239 first-year males, we hypothesized that participants would increase drinking from pre-college to the first month of college. Results reveal a general trend toward increased drinking upon entering college. Caucasians increased…

  13. Changes in neural mechanisms of cognitive control during the transition from late adolescence to young adulthood

    NARCIS (Netherlands)

    Veroude, K.; Jolles, J.; Croiset, G.; Krabbendam, L.

    2013-01-01

    The transition from late adolescence to young adulthood is marked by anatomical maturation of various brain regions. In parallel, defining life changes take place, such as entrance into college. Up till now research has not focused on functional brain differences during this particular developmental

  14. 77 FR 7080 - Changes To Implement Transitional Program for Covered Business Method Patents

    Science.gov (United States)

    2012-02-10

    ... Patent and Trademark Office 37 CFR Part 42 RIN 0651-AC73 Changes To Implement Transitional Program for Covered Business Method Patents AGENCY: United States Patent and Trademark Office, Commerce. ACTION: Notice of proposed rulemaking. SUMMARY: The United States Patent and Trademark Office (Office or USPTO...

  15. The effects of internationalization, intangible resources and technological change on the transition to a multiproduct company

    National Research Council Canada - National Science Library

    Moisés Alejandro Alarcón Osuna; Carlos Fong Reynoso; Luis Ernesto Ocampo Figueroa

    2017-01-01

    .... The results show that the accumulation of intangibles, such as human capital, allows a transition to a multi-product company, but the effect of this accumulation is higher in an internationalized company. In addition, technological change creates incentives to not move to a multi-product company, where this effect is greater in an internationalized company.

  16. Glass heat capacity and its abrupt change in glass transition region

    DEFF Research Database (Denmark)

    Yue, Yuanzheng; Smedskjær, Morten Mattrup; Mauro, John C.

    Glass transition (GT) has been a fascinating, but challenging subject in the condensed matter science over decades. Despite progress in understanding GT, many crucial problems still need to be clarified. One of the problems deals with the microscopic origin of abrupt change of heat capacity (Cp) ...

  17. Evidence that Implementation Intentions Promote Transitions Between the Stages of Change

    Science.gov (United States)

    Armitage, Christopher J.

    2006-01-01

    A dietary change intervention based on Gollwitzer's (1993) concept of implementation intentions was used to see whether transitions between transtheoretical model stages could be induced in a field experiment. Participants (N = 554) were randomized to receive either questionnaire-only or questionnaire-plus-implementation intention. Results showed…

  18. Lifestyle interventions targeting body weight changes during the menopause transition: a systematic review.

    Science.gov (United States)

    Jull, Janet; Stacey, Dawn; Beach, Sarah; Dumas, Alex; Strychar, Irene; Ufholz, Lee-Anne; Prince, Stephanie; Abdulnour, Joseph; Prud'homme, Denis

    2014-01-01

    To determine the effectiveness of exercise and/or nutrition interventions and to address body weight changes during the menopause transition. A systematic review of the literature was conducted using electronic databases, grey literature, and hand searching. Two independent researchers screened for studies using experimental designs to evaluate the impact of exercise and/or nutrition interventions on body weight and/or central weight gain performed during the menopausal transition. Studies were quality appraised using Cochrane risk of bias. Included studies were analyzed descriptively. Of 3,564 unique citations screened, 3 studies were eligible (2 randomized controlled trials, and 1 pre/post study). Study quality ranged from low to high risk of bias. One randomized controlled trial with lower risk of bias concluded that participation in an exercise program combined with dietary interventions might mitigate body adiposity increases, which is normally observed during the menopause transition. The other two studies with higher risk of bias suggested that exercise might attenuate weight loss or weight gain and change abdominal adiposity patterns. High quality studies evaluating the effectiveness of interventions targeting body weight changes in women during their menopause transition are needed. Evidence from one higher quality study indicates an effective multifaceted intervention for women to minimize changes in body adiposity.

  19. Changes in primary health care centres over the transition period in Slovenia.

    NARCIS (Netherlands)

    Albreht, T.; Delnoij, D.M.J.; Klazinga, N.

    2006-01-01

    BACKGROUND: Primary health care centres (PHCCs) were a characteristic of the former Yugoslav health care system introduced widely in Slovenia. Transition brought structural changes to health care and the position of the PHCC's was challenged. This paper investigates (i) PHCCs' perception of

  20. Coping across the Transition to Adolescence: Evidence of Interindividual Consistency and Mean-Level Change

    Science.gov (United States)

    Valiente, Carlos; Eisenberg, Nancy; Fabes, Richard A.; Spinrad, Tracy L.; Sulik, Michael J.

    2015-01-01

    The goal of this study was to examine various forms of coping across the transition to adolescence, with a focus on interindividual (correlational) consistency of coping and mean-level changes in coping. Adolescents' emotional coping, problem solving, positive cognitive restructuring, avoidance, and support seeking in response to everyday…

  1. Tracking excited-state charge and spin dynamics in iron coordination complexes

    DEFF Research Database (Denmark)

    Zhang, Wenkai; Alonso-Mori, Roberto; Bergmann, Uwe

    2014-01-01

    Crucial to many light-driven processes in transition metal complexes is the absorption and dissipation of energy by 3d electrons(1-4). But a detailed understanding of such non-equilibrium excited-state dynamics and their interplay with structural changes is challenging: a multitude of excited...... states and possible transitions result in phenomena too complex to unravel when faced with the indirect sensitivity of optical spectroscopy to spin dynamics(5) and the flux limitations of ultrafast X-ray sources(6,7). Such a situation exists for archetypal poly-pyridyl iron complexes, such as [Fe(2......,2'-bipyridine)(3)](2+), where the excited-state charge and spin dynamics involved in the transition from a low-to a high-spin state (spin crossover) have long been a source of interest and controversy(6-15). Here we demonstrate that femtosecond resolution X-ray fluorescence spectroscopy, with its sensitivity...

  2. Observation of the spin Nernst effect

    Science.gov (United States)

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

    2017-10-01

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

  3. Changes in academic efficacy during the transition from elementary school to secondary school

    OpenAIRE

    Lávičková, Soňa

    2016-01-01

    The focus of this work is a description of changes in the academic self-efficacy among adolescents when they change school environment and demands of studies. Academic self- efficacy is defined as one of the predictors of school achievement. In the theoretical part, there are summarized results of foreign researches which describe the development of academic self-efficacy during school attendance. This work focuses especially on transition from elementary to high school. Moreover, there are m...

  4. Changes in the Indonesian Throughflow and southeast Asian hydroclimate during the Middle-Miocene Climate Transition

    Science.gov (United States)

    Frigola Boix, Amanda; Prange, Matthias; Schulz, Michael

    2013-04-01

    The present-day Indonesian Throughflow (ITF), a key component in the global ocean circulation, transports relatively cold low-salinity water from the Pacific to the Indian oceans. This ocean current is of course not a constant system, meaning that its characteristics have changed throughout its history, both due to local forcings, such as changes in the geometry of the passages, and changes in the global climate system, such as the Middle-Miocene Climate Transition. The Middle-Miocene Climate Transition leads from the warm Middle-Miocene Climatic Optimum into the subsequent "icehouse world". The transition is associated with an increase in Antarctic glaciation at ~13.9 Ma. The aim of this study is to investigate the differences in atmospheric and ocean circulation between the warm and cold climate states in the Middle Miocene, specifically on changes in the characteristics of the ITF and shifts in the tropical rainbelt. We test whether there was a northward movement of the tropical rainbelt in southeast Asia as has been suggested on the basis of palaeoclimatic proxy records. We employ the comprehensive Community Climate System Model (CCSM) version 3.0 in a medium resolution. All the experiments used Miocene boundary conditions, including topography, bathymetry and vegetation. Two simulations were carried out, representing the time before and after the climate transition. Different boundary conditions take into account changes in ice-sheet geometry, sea-level and atmospheric CO2 concentration. The state prior to the transition is characterized by Antarctica being partially glaciated, with one ice cap covering the Transantarctic Mountains and another over East Antarctica. The second simulation corresponds to a fully glaciated Antarctica with one single merged ice-sheet covering the whole continent. We will present initial analyses of hydrological fields and ocean circulation to assess the role of Antarctic glaciation on tropical climate.

  5. SU-D-18C-05: Variable Bolus Arterial Spin Labeling MRI for Accurate Cerebral Blood Flow and Arterial Transit Time Mapping

    Energy Technology Data Exchange (ETDEWEB)

    Johnston, M; Jung, Y [Wake Forest School of Medicine, Winston-Salem, NC (United States)

    2014-06-01

    Purpose: Arterial spin labeling (ASL) is an MRI perfusion imaging method from which quantitative cerebral blood flow (CBF) maps can be calculated. Acquisition with variable post-labeling delays (PLD) and variable TRs allows for arterial transit time (ATT) mapping and leads to more accurate CBF quantification with a scan time saving of 48%. In addition, T1 and M0 maps can be obtained without a separate scan. In order to accurately estimate ATT and T1 of brain tissue from the ASL data, variable labeling durations were invented, entitled variable-bolus ASL. Methods: All images were collected on a healthy subject with a 3T Siemens Skyra scanner. Variable-bolus Psuedo-continuous ASL (PCASL) images were collected with 7 TI times ranging 100-4300ms in increments of 700ms with TR ranging 1000-5200ms. All boluses were 1600ms when the TI allowed, otherwise the bolus duration was 100ms shorter than the TI. All TI times were interleaved to reduce sensitivity to motion. Voxel-wise T1 and M0 maps were estimated using a linear least squares fitting routine from the average singal from each TI time. Then pairwise subtraction of each label/control pair and averaging for each TI time was performed. CBF and ATT maps were created using the standard model by Buxton et al. with a nonlinear fitting routine using the T1 tissue map. Results: CBF maps insensitive to ATT were produced along with ATT maps. Both maps show patterns and averages consistent with literature. The T1 map also shows typical T1 contrast. Conclusion: It has been demonstrated that variablebolus ASL produces CBF maps free from the errors due to ATT and tissue T1 variations and provides M0, T1, and ATT maps which have potential utility. This is accomplished with a single scan in a feasible scan time (under 6 minutes) with low sensivity to motion.

  6. Spin-polarized x-ray emission of 3d transition-metal ions : A comparison via K alpha and K beta detection

    NARCIS (Netherlands)

    Wang, Xin; deGroot, F.M.F.; Cramer, SP

    1997-01-01

    This paper demonstrates that spin-polarized x-ray-excitation spectra can be obtained using K alpha emission as well as K beta lines. A spin-polarized analysis of K alpha x-ray emission and the excitation spectra by K alpha detection on a Ni compound is reported. A systematic analysis of the

  7. Empirical models of transitions between coral reef states: effects of region, protection, and environmental change.

    Science.gov (United States)

    Lowe, Phillip K; Bruno, John F; Selig, Elizabeth R; Spencer, Matthew

    2011-01-01

    There has been substantial recent change in coral reef communities. To date, most analyses have focussed on static patterns or changes in single variables such as coral cover. However, little is known about how community-level changes occur at large spatial scales. Here, we develop Markov models of annual changes in coral and macroalgal cover in the Caribbean and Great Barrier Reef (GBR) regions. We analyzed reef surveys from the Caribbean and GBR (1996-2006). We defined a set of reef states distinguished by coral and macroalgal cover, and obtained Bayesian estimates of the annual probabilities of transitions between these states. The Caribbean and GBR had different transition probabilities, and therefore different rates of change in reef condition. This could be due to differences in species composition, management or the nature and extent of disturbances between these regions. We then estimated equilibrium probability distributions for reef states, and coral and macroalgal cover under constant environmental conditions. In both regions, the current distributions are close to equilibrium. In the Caribbean, coral cover is much lower and macroalgal cover is higher at equilibrium than in the GBR. We found no evidence for differences in transition probabilities between the first and second halves of our survey period, or between Caribbean reefs inside and outside marine protected areas. However, our power to detect such differences may have been low. We also examined the effects of altering transition probabilities on the community state equilibrium, along a continuum from unfavourable (e.g., increased sea surface temperature) to favourable (e.g., improved management) conditions. Both regions showed similar qualitative responses, but different patterns of uncertainty. In the Caribbean, uncertainty was greatest about effects of favourable changes, while in the GBR, we are most uncertain about effects of unfavourable changes. Our approach could be extended to provide

  8. Empirical models of transitions between coral reef states: effects of region, protection, and environmental change.

    Directory of Open Access Journals (Sweden)

    Phillip K Lowe

    Full Text Available There has been substantial recent change in coral reef communities. To date, most analyses have focussed on static patterns or changes in single variables such as coral cover. However, little is known about how community-level changes occur at large spatial scales. Here, we develop Markov models of annual changes in coral and macroalgal cover in the Caribbean and Great Barrier Reef (GBR regions. We analyzed reef surveys from the Caribbean and GBR (1996-2006. We defined a set of reef states distinguished by coral and macroalgal cover, and obtained Bayesian estimates of the annual probabilities of transitions between these states. The Caribbean and GBR had different transition probabilities, and therefore different rates of change in reef condition. This could be due to differences in species composition, management or the nature and extent of disturbances between these regions. We then estimated equilibrium probability distributions for reef states, and coral and macroalgal cover under constant environmental conditions. In both regions, the current distributions are close to equilibrium. In the Caribbean, coral cover is much lower and macroalgal cover is higher at equilibrium than in the GBR. We found no evidence for differences in transition probabilities between the first and second halves of our survey period, or between Caribbean reefs inside and outside marine protected areas. However, our power to detect such differences may have been low. We also examined the effects of altering transition probabilities on the community state equilibrium, along a continuum from unfavourable (e.g., increased sea surface temperature to favourable (e.g., improved management conditions. Both regions showed similar qualitative responses, but different patterns of uncertainty. In the Caribbean, uncertainty was greatest about effects of favourable changes, while in the GBR, we are most uncertain about effects of unfavourable changes. Our approach could be

  9. A Diagnostic Procedure for Transformative Change Based on Transitions, Resilience, and Institutional Thinking

    Directory of Open Access Journals (Sweden)

    Briony C. Ferguson

    2013-12-01

    Full Text Available Urban water governance regimes around the world have traditionally planned large-scale, centralized infrastructure systems that aim to control variables and reduce uncertainties. There is growing sectoral awareness that a transition toward sustainable alternatives is necessary if systems are to meet society's future water needs in the context of drivers such as climate change and variability, demographic changes, environmental degradation, and resource scarcity. However, there is minimal understanding of how the urban water sector should operationalize its strategic planning for such change to facilitate the transition to a sustainable water future. We have integrated concepts from transitions, resilience, and institutional theory to develop a diagnostic procedure for revealing insights into which types of strategic action are most likely to influence the direction and pace of change in the overall system toward a desired trajectory. The procedure used the multipattern approach, from transition theory, to identify the system conditions and type of changes necessary for enabling system transformation. It incorporated the adaptive cycle, from resilience theory, to identify the current phase of change for different parts of the system. Finally, it drew on the concepts of institutional pillars and institutional work to identify mechanisms that are likely to be most effective in influencing the transformative dynamics of the system toward a desired trajectory. We have demonstrated application of the proposed diagnostic procedure on a case study of recent transformative change in the urban water system of Melbourne, Australia. We have proposed that an operational diagnostic procedure provides a useful platform from which planners, policy analysts, and decision makers could follow a process of deduction that identifies which types of strategic action best fit the current system conditions.

  10. The local atomic structure of La{sub 1{minus}x}Sr{sub x}CoO{sub 3}: Effects induced by the spin-state and non-metal to metal transitions

    Energy Technology Data Exchange (ETDEWEB)

    Louca, D.; Sarrao, J.L.; Kwei, G.H.

    1998-03-01

    The pair density function (PDF) used in the analysis of pulsed neutron diffraction data of La{sub 1{minus}x}Sr{sub x}CoO{sub 3} revealed new structural effects which are correlated to the susceptibility and transport transitions. The transition in the spin configuration of the Co ions from the low-spin (LS) to the high-spin (HS) state in the Co perovskite oxides can potentially induce structural distortions due to the coupling of the spin to the lattice and charge. The ground state of the pure compound, LaCoO{sub 3}, is in the LS state and is non-magnetic. A transition occurs to the HS state at {approximately} 50 K as indicated from the susceptibility measurements due to the thermal excitation of electrons to the e{sub g} level. The Co{sub LS}O{sub 6} octahedra associated with the Co ions in the LS configuration are distinguished from the Co{sub HS}O{sub 6} octahedra with the Co in the HS configuration because the Co{sub LS}-O bond length is shorter than the Co{sub HS}-O distance due to the different size of the corresponding Co ions. Such bond lengths are clearly identified in the local structure between 15--300 K. This finding is in contrast to the average structure which shows only one type of bond length in this temperature range but two types of bond lengths are suggested at considerably higher temperatures. This suggests that whereas the LS and HS CoO{sub 6}-octahedra coexist, they are randomly distributed in the crystal lattice at lower temperatures and become ordered at higher temperatures.

  11. Finite-temperature coupled-cluster, many-body perturbation, and restricted and unrestricted Hartree-Fock study on one-dimensional solids: Luttinger liquids, Peierls transitions, and spin- and charge-density waves

    Science.gov (United States)

    Hermes, Matthew R.; Hirata, So

    2015-09-01

    One-dimensional (1D) solids exhibit a number of striking electronic structures including charge-density wave (CDW) and spin-density wave (SDW). Also, the Peierls theorem states that at zero temperature, a 1D system predicted by simple band theory to be a metal will spontaneously dimerize and open a finite fundamental bandgap, while at higher temperatures, it will assume the equidistant geometry with zero bandgap (a Peierls transition). We computationally study these unique electronic structures and transition in polyyne and all-trans polyacetylene using finite-temperature generalizations of ab initio spin-unrestricted Hartree-Fock (UHF) and spin-restricted coupled-cluster doubles (CCD) theories, extending upon previous work [He et al., J. Chem. Phys. 140, 024702 (2014)] that is based on spin-restricted Hartree-Fock (RHF) and second-order many-body perturbation (MP2) theories. Unlike RHF, UHF can predict SDW as well as CDW and metallic states, and unlike MP2, CCD does not diverge even if the underlying RHF reference wave function is metallic. UHF predicts a gapped SDW state with no dimerization at low temperatures, which gradually becomes metallic as the temperature is raised. CCD, meanwhile, confirms that electron correlation lowers the Peierls transition temperature. Furthermore, we show that the results from all theories for both polymers are subject to a unified interpretation in terms of the UHF solutions to the Hubbard-Peierls model using different values of the electron-electron interaction strength, U/t, in its Hamiltonian. The CCD wave function is shown to encompass the form of the exact solution of the Tomonaga-Luttinger model and is thus expected to describe accurately the electronic structure of Luttinger liquids.

  12. Finite-temperature coupled-cluster, many-body perturbation, and restricted and unrestricted Hartree–Fock study on one-dimensional solids: Luttinger liquids, Peierls transitions, and spin- and charge-density waves

    Energy Technology Data Exchange (ETDEWEB)

    Hermes, Matthew R. [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States); Hirata, So, E-mail: sohirata@illinois.edu [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States); CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan)

    2015-09-14

    One-dimensional (1D) solids exhibit a number of striking electronic structures including charge-density wave (CDW) and spin-density wave (SDW). Also, the Peierls theorem states that at zero temperature, a 1D system predicted by simple band theory to be a metal will spontaneously dimerize and open a finite fundamental bandgap, while at higher temperatures, it will assume the equidistant geometry with zero bandgap (a Peierls transition). We computationally study these unique electronic structures and transition in polyyne and all-trans polyacetylene using finite-temperature generalizations of ab initio spin-unrestricted Hartree–Fock (UHF) and spin-restricted coupled-cluster doubles (CCD) theories, extending upon previous work [He et al., J. Chem. Phys. 140, 024702 (2014)] that is based on spin-restricted Hartree–Fock (RHF) and second-order many-body perturbation (MP2) theories. Unlike RHF, UHF can predict SDW as well as CDW and metallic states, and unlike MP2, CCD does not diverge even if the underlying RHF reference wave function is metallic. UHF predicts a gapped SDW state with no dimerization at low temperatures, which gradually becomes metallic as the temperature is raised. CCD, meanwhile, confirms that electron correlation lowers the Peierls transition temperature. Furthermore, we show that the results from all theories for both polymers are subject to a unified interpretation in terms of the UHF solutions to the Hubbard–Peierls model using different values of the electron-electron interaction strength, U/t, in its Hamiltonian. The CCD wave function is shown to encompass the form of the exact solution of the Tomonaga–Luttinger model and is thus expected to describe accurately the electronic structure of Luttinger liquids.

  13. Psychosocial changes following transition to an aged care home: qualitative findings from Iran.

    Science.gov (United States)

    Zamanzadeh, Vahid; Rahmani, Azad; Pakpour, Vahid; Chenoweth, Lynnette Lorraine; Mohammadi, Eesa

    2017-06-01

    The study explored the psychosocial effects of transitioning from home to an aged care home for older Iranian people. Moving from one's own home to a communal aged care home is challenging for older people and may give rise to numerous psychosocial responses. The extent and intensity of such changes have rarely been explored in Middle Eastern countries. Data were collected through purposive sampling by in-depth semi-structured interviews with 20 participants (17 people living in aged care homes and three formal caregivers). All the interviews were recorded and typed, and conventional qualitative content analysis was used, eliciting common themes. There were four common themes: communication isolation, resource change, monotone institutional life and negative emotional response. Participants lost their previous support systems when transitioning to an aged care home and were not able to establish new ones. Routine care was provided by formal caregivers with little attention to individual needs, and minimal support was given to help maintain the older person's independence. These losses gave rise to negative emotions in some of the participants, depending on their previous lifestyle and accommodation arrangements. The extent and intensity of psychosocial changes occurring in most of the participants following their transition to an aged care home indicates the need for a review of Iranian aged care services. To assist older Iranian people adapt more readily when making the transition to aged care home and to meet their unique psychosocial needs, a family-centred approach to service delivery is recommended. © 2016 John Wiley & Sons Ltd.

  14. Positive Developmental Changes after Transition to High School: Is Retrospective Growth Correlated with Measured Changes in Current Status of Personal Growth?

    Science.gov (United States)

    Iimura, Shuhei; Taku, Kanako

    2018-02-14

    The transition to high school is generally considered as a stressful turning point in adolescent development, but some students experience personal growth (i.e., positive developmental changes) through that experience. It is important to examine the mechanism behind such positive changes to understand various developmental patterns of adolescents during the transition. However, the concept of growth in this research area remains unexplored. Some researchers have questioned whether retrospective, self-reported growth reflects actual positive changes in the perception of personal growth. We elaborated on the concept of growth after high school transition by examining whether retrospective appraisal of personal growth after transition to high school is correlated with measured change in growth. Two hundred and sixty-two Japanese adolescents (aged 14-16 years, 50% girls) participated in surveys right before and right after transition. We assessed five domains of growth, including improved relating to others, identification of new possibilities, increased sense of personal strength, spiritual growth, and greater appreciation of life. The results showed that retrospective assessment of growth and measured change during transition were positively associated, provided the adolescents reported the transition as an important turning point in their lives. Adolescents who experienced salient positive changes across the transition were more likely to engage in intrusive and deliberate rumination and social support than adolescents who reported fewer changes. In summary, retrospective growth covaried with measured change only when adolescents perceived the transition as impactful in their lives.

  15. PREFACE: Spin Electronics

    Science.gov (United States)

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

    2007-04-01

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

  16. State-and-transition simulation models: a framework for forecasting landscape change

    Science.gov (United States)

    Daniel, Colin; Frid, Leonardo; Sleeter, Benjamin M.; Fortin, Marie-Josée

    2016-01-01

    SummaryA wide range of spatially explicit simulation models have been developed to forecast landscape dynamics, including models for projecting changes in both vegetation and land use. While these models have generally been developed as separate applications, each with a separate purpose and audience, they share many common features.We present a general framework, called a state-and-transition simulation model (STSM), which captures a number of these common features, accompanied by a software product, called ST-Sim, to build and run such models. The STSM method divides a landscape into a set of discrete spatial units and simulates the discrete state of each cell forward as a discrete-time-inhomogeneous stochastic process. The method differs from a spatially interacting Markov chain in several important ways, including the ability to add discrete counters such as age and time-since-transition as state variables, to specify one-step transition rates as either probabilities or target areas, and to represent multiple types of transitions between pairs of states.We demonstrate the STSM method using a model of land-use/land-cover (LULC) change for the state of Hawai'i, USA. Processes represented in this example include expansion/contraction of agricultural lands, urbanization, wildfire, shrub encroachment into grassland and harvest of tree plantations; the model also projects shifts in moisture zones due to climate change. Key model output includes projections of the future spatial and temporal distribution of LULC classes and moisture zones across the landscape over the next 50 years.State-and-transition simulation models can be applied to a wide range of landscapes, including questions of both land-use change and vegetation dynamics. Because the method is inherently stochastic, it is well suited for characterizing uncertainty in model projections. When combined with the ST-Sim software, STSMs offer a simple yet powerful means for developing a wide range of models of

  17. Changes in the composition of synthesis products upon transitioning from self-ignition to combustion

    Science.gov (United States)

    Seplyarskii, B. S.; Ivleva, T. P.; Grachev, V. V.; Merzhanov, A. G.

    2017-07-01

    Changes in the chemical composition of condensed products upon switching from synthesis in the self-ignition mode to combustion synthesis is studied by approximate analytical and numerical means for condensed substances that react via competing reaction pathways. It is shown that these different modes of synthesis produce different compositions of the reaction products. The conditions required for transitioning from one mode of combustion initiation (thermal explosion) to another (ignition) are determined. It is found that this transition can occur upon changing the temperature of a heater by just two characteristic intervals. A scaling procedure that allows the calculation results obtained at zero dimensionless temperature of the heater to be used to determine the effect its non-zero dimensionless temperature has on the ignition mode and the composition of the obtained products is proposed. Calculations show that materials with different distributions of the chemical composition along the sample can be obtained by deliberately changing the temperature of the heater.

  18. Changes in Sleep Duration and Sleep Timing Associated with Retirement Transitions.

    Science.gov (United States)

    Hagen, Erika W; Barnet, Jodi H; Hale, Lauren; Peppard, Paul E

    2016-03-01

    Investigate whether retirement transitions are associated with changes in sleep duration and sleep timing, and whether these associations are modified by age, sex, mental health, or circadian preference. The Retirement and Sleep Trajectories (REST) study is a longitudinal study consisting of four annual mailed surveys that collected information about employment, sleep, and health. Differences in reported sleep duration, bedtime and wake time between successive surveys were calculated to estimate change over 1, 2, and 3 y. Linear regression models were used to estimate changes in these sleep parameters associated with retirement 1, 2, and 3 y posttransition. Retiring from full-time work was associated with bedtimes that were 30, 31, and 36 min later 1, 2, and 3 y postretirement; wake times that were 63, 69, and 78 min later; and sleep durations that were 15, 16, and 22 min longer 1, 2, and 3 y postretirement. These associations did not differ by sex or mental health status. Age and circadian preference modified the associations between retirement and change in sleep parameters; the increase in sleep duration was shorter and the wake time extension was lesser with advancing retirement age; those with evening preference had longer wake time extensions than those with morning preference. Transitioning to retirement is associated with longer sleep duration, later bedtimes, and later wake times. These changes were detectable about 1 y postwork transition and were persistent up to 3 y later. © 2016 Associated Professional Sleep Societies, LLC.

  19. Vacuum spin squeezing

    Science.gov (United States)

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

    2017-11-01

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

  20. Crossover from Spin Accumulation into Interface States to Spin Injection in the Germanium Conduction Band

    Science.gov (United States)

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

    2013-03-01

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

  1. Modelled ocean changes at the Plio-Pleistocene transition driven by Antarctic ice advance.

    Science.gov (United States)

    Hill, Daniel J; Bolton, Kevin P; Haywood, Alan M

    2017-03-02

    The Earth underwent a major transition from the warm climates of the Pliocene to the Pleistocene ice ages between 3.2 and 2.6 million years ago. The intensification of Northern Hemisphere Glaciation is the most obvious result of the Plio-Pleistocene transition. However, recent data show that the ocean also underwent a significant change, with the convergence of deep water mass properties in the North Pacific and North Atlantic Ocean. Here we show that the lack of coastal ice in the Pacific sector of Antarctica leads to major reductions in Pacific Ocean overturning and the loss of the modern North Pacific Deep Water (NPDW) mass in climate models of the warmest periods of the Pliocene. These results potentially explain the convergence of global deep water mass properties at the Plio-Pleistocene transition, as Circumpolar Deep Water (CDW) became the common source.

  2. Changes in Physical Activity and Function with Transition to Retirement Living: A Pilot Study.

    Science.gov (United States)

    Regan, Kayla; Intzandt, Brittany; Swatridge, Karli; Myers, Anita; Roy, Eric; Middleton, Laura E

    2016-12-01

    This pilot study examined changes in physical activity and function among older adults moving from community dwellings to retirement living. Twelve community-dwelling older adults, recruited from the wait-lists of two retirement living facilities, were assessed prior to and following the transition to retirement living. Physical activity was assessed using an Actigraph (GT3X+) activity monitor; physical activity by type was reported with the CHAMPS activity questionnaire. Physical function was assessed using the Senior Fitness Test. Objectively monitored total physical activity decreased after the transition to retirement living (p = 0.02). Reports of physical activity by type indicated that only activities of daily living decreased (p < 0.01) although intentional exercise increased (p < 0.03) with the transition. Endurance and strength also improved (p < 0.05 and p < 0.04). Pilot results indicate that possible physical benefits accrue from retirement living, although efforts to reduce sedentary time are needed.

  3. Incremental change, transition or transformation? optimising change pathways for climate adaptation in spatial planning

    NARCIS (Netherlands)

    Roggema, R.E.; Vermeend, T.; Van den Dobbelsteen, A.A.J.F.

    2012-01-01

    In order to incorporate climate adaptation in spatial planning change is required, because climate change impacts the way we live. This implies that spatial planning, as the arranger of the spatial organisation and layout needs to be able to support this change. Current spatial planning is not yet

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

    DEFF Research Database (Denmark)

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

    2000-01-01

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

  5. Changes in depression among older adults in China: A latent transition analysis.

    Science.gov (United States)

    Ni, Yuhan; Tein, Jenn-Yun; Zhang, Minqiang; Yang, Yawei; Wu, Guoting

    2017-02-01

    Depression in late life is an important public health problem in developing countries. It is timely to investigate stability and transition patterns of depressive symptom subtypes. Longitudinal data were used from the China Health and Retirement Longitudinal Study (CHARLS). A total of 853 women and 930 men aged 60-96 years were recruited. Latent class and latent transition analysis (LCA/LTA) were used to identify meaningful subgroups, transitions between those classes across time, and baseline demographic features that help to predict and design tailored interventions. Three depression subgroups were identified: Class 1 was labeled "Mild Depression"; Class 2 was labeled "Severe Depression" and class 3 was labeled "Lack of Positive Affect". A predominant tendency for stability appeared rather than change, meanwhile individual in Mild Depression and Severe Depression latent status both had a high probability to convert to the Lack of Positive Affect latent status. Social activities played a significant role in buffering the effect of depression, while individuals with chronic diseases, having difficulty with ADLs and smoking might be at-risk groups. The limitations of the present study were inherent limitation in the LTA model and some small proportion of transitions. This study demonstrated a transition pattern in older adult depression within a person-centered approach. Differential treatment effects were found across baseline depression class, suggesting the benefit for tailored intervention programs to improve depression outcomes among older adults. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Topological Order in Spin Liquids with Chirality

    OpenAIRE

    Scharfenberger, Burkhard

    2011-01-01

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

  7. Changing transport and traffic risks - a CliPDaR spin off

    Science.gov (United States)

    Matulla, Christoph; Namyslo, Joachim; Gringinger, Julia; Andre, Konrad; Chimani, Barbara; Hollosi, Brigitta; Mlinar, Christian; Gschier, Roland; Fuchs, Tobias; Auer, Inge

    2014-05-01

    The delivery of goods, people's mobility, the supply with services and the free accessibility of vital resources, as hospitals for instance, are indispensable for our society. All that is possible through functioning transport networks. Globalisation, changes in technology, demography and climate as well as the strong increase in freight traffic are fundamental challenges to the reinforcement of systems in place and the planning of future transport corridors. As for climate change we present an approach to estimate the rate and amount of change than has to be managed in the future by the transport authorities. This assessment is based on combinations of weather elements that potentially harm the transport system. Such combinations (called climate indices, CIs) are evaluated for the past and the future. The evaluation of the past is done by the use of observations; the assessment of the future is based on ensembles of scenario projections, since a single projection does not allow deriving uncertainty based statements. Landslides originating from long term rain events may serve as an example. In 2013 a number of landslides caused substantial destruction and downtimes in turn. The perhaps most prominent example took place in Tirol where the Felbertauern road was hit twice by landslides and the avalanche gallery was destroyed. In our presentation at the EGU we will show changes in CIs that are related to landslides, rutting, frost thaw cycles (e.g. responsible for falling roks) and heavy precipitation events (potentially important for the flooding of transport assets as tunnels and drainage systems or dangerous to bridges). These changes refer to two future periods: the near future (2021-2050) and the remote future (2071-2100); and they refer to the climatological normal period (19961-1990). Referring to landslides there are regions showing no change and other areas with substantial increases, which predominantly occur close to topographic complex terrain. Such regions

  8. Spin-Hall magnetoresistance and spin Seebeck effect in spin-spiral and paramagnetic phases of multiferroic CoCr2O4 films

    NARCIS (Netherlands)

    Aqeel, A.; Vlietstra, N.; Heuver, J.A.; Bauer, G.E.W.; Noheda, B.; Van Wees, B.J.; Palstra, T.T.M.

    2015-01-01

    We report on the spin-Hall magnetoresistance (SMR) and spin Seebeck effect (SSE) in multiferroic CoCr2O4 (CCO) spinel thin films with Pt contacts. We observe a large enhancement of both signals below the spin-spiral (Ts=28K) and the spin lock-in (Tlock?in=14K) transitions. The SMR and SSE responses

  9. Spin-Hall magnetoresistance and spin Seebeck effect in spin-spiral and paramagnetic phases of multiferroic CoCr2O4 films

    NARCIS (Netherlands)

    Aqeel, A.; Vlietstra, N.; Heuver, J. A.; Bauer, G. E. W.; Noheda, B.; van Wees, B. J.; Palstra, T. T. M.

    2015-01-01

    We report on the spin-Hall magnetoresistance (SMR) and spin Seebeck effect (SSE) in multiferroic CoCr2O4 (CCO) spinel thin films with Pt contacts. We observe a large enhancement of both signals below the spin-spiral (T-s = 28 K) and the spin lock-in (Tlock-in = 14 K) transitions. The SMR and SSE

  10. Integrating continuous stocks and flows into state-and-transition simulation models of landscape change

    Science.gov (United States)

    Daniel, Colin J.; Sleeter, Benjamin M.; Frid, Leonardo; Fortin, Marie-Josée

    2017-01-01

    State-and-transition simulation models (STSMs) provide a general framework for forecasting landscape dynamics, including projections of both vegetation and land-use/land-cover (LULC) change. The STSM method divides a landscape into spatially-referenced cells and then simulates the state of each cell forward in time, as a discrete-time stochastic process using a Monte Carlo approach, in response to any number of possible transitions. A current limitation of the STSM method, however, is that all of the state variables must be discrete.Here we present a new approach for extending a STSM, in order to account for continuous state variables, called a state-and-transition simulation model with stocks and flows (STSM-SF). The STSM-SF method allows for any number of continuous stocks to be defined for every spatial cell in the STSM, along with a suite of continuous flows specifying the rates at which stock levels change over time. The change in the level of each stock is then simulated forward in time, for each spatial cell, as a discrete-time stochastic process. The method differs from the traditional systems dynamics approach to stock-flow modelling in that the stocks and flows can be spatially-explicit, and the flows can be expressed as a function of the STSM states and transitions.We demonstrate the STSM-SF method by integrating a spatially-explicit carbon (C) budget model with a STSM of LULC change for the state of Hawai'i, USA. In this example, continuous stocks are pools of terrestrial C, while the flows are the possible fluxes of C between these pools. Importantly, several of these C fluxes are triggered by corresponding LULC transitions in the STSM. Model outputs include changes in the spatial and temporal distribution of C pools and fluxes across the landscape in response to projected future changes in LULC over the next 50 years.The new STSM-SF method allows both discrete and continuous state variables to be integrated into a STSM, including interactions between

  11. Hypoxia, Epithelial-Mesenchymal Transition, and TET-Mediated Epigenetic Changes

    Directory of Open Access Journals (Sweden)

    Shih-Han Kao

    2016-02-01

    Full Text Available Tumor hypoxia is a pathophysiologic outcome of disrupted microcirculation with inadequate supply of oxygen, leading to enhanced proliferation, epithelial-mesenchymal transition (EMT, metastasis, and chemo-resistance. Epigenetic changes induced by hypoxia are well documented, and they lead to tumor progression. Recent advances show that DNA demethylation mediated by the Ten-eleven translocation (TET proteins induces major epigenetic changes and controls key steps of cancer development. TET enzymes serve as 5mC (5-methylcytosine-specific dioxygenases and cause DNA demethylation. Hypoxia activates the expression of TET1, which also serves as a co-activator of HIF-1α transcriptional regulation to modulate HIF-1α downstream target genes and promote epithelial-mesenchymal transition. As HIF is a negative prognostic factor for tumor progression, hypoxia-activated prodrugs (HAPs may provide a favorable therapeutic approach to lessen hypoxia-induced malignancy.

  12. Institutional Change and Governance Indexes in Transition Economies: the case of Poland

    Directory of Open Access Journals (Sweden)

    Pasquale Tridico

    2006-12-01

    Full Text Available In the former communist countries, institutional change, i.e. transition towards market economy, is affected not only by introduction of law and formal institutions (change "by design", but also by social norms, old values and habits (informal institutions. I present an empirical paper focusing on transition of the Polish Economy. I used a questionnaire which was administered to a sample of about 1000 Polish firms in order to verify the impact of economic institutions on the "residual productivity". Throughout the questionnaire I built six governance indexes. Then I tested the impact of the governance indexes on the productivity of firms. I observed that the economic performance of the eastern regions of Poland, where governance indexes are worse than western, are poorer than that of the western regions of Poland

  13. Synchrotron radiation structure analyses of the light-induced radical pair of a hexaarylbiimidazolyl derivative. Origin of the spin-multiplicity change

    CERN Document Server

    Kawano, M; Matsubara, K; Imabayashi, H; Mitsumi, M; Toriumi, K; Ohashi, Y

    2002-01-01

    In situ synchrotron radiation structure analyses of a light-induced radical pair from o-Cl-HABI were performed by using an X-ray vacuum camera at 23-70K at the BL02B1 station of SPring-8. The combined results of X-ray analysis with theoretical calculation, IR, and UV-vis spectroscopy reveal that a slight conformational change of the radical pair causes the drastic spin-multiplicity change during 2-140K. (author)

  14. Measurement of transition quadrupole moments of high-spin states in the N=74 isotones sup 1 sup 3 sup 3 Pr, sup 1 sup 3 sup 2 Ce and sup 1 sup 3 sup 1 La

    CERN Document Server

    Paul, E S; Gizon, J; Hauschild, K; Hibbert, I M; Joss, D T; Nolan, P J; Nyakó, B M; Sampson, J A; Semple, A T; Wadsworth, R; Walker, L; Wilson, J N; Zolnai, L

    2001-01-01

    The Doppler-Shift Attenuation Method has been used to extract transition quadrupole moments of high-spin bands in the N=74 isotones sup 1 sup 3 sup 3 Pr, sup 1 sup 3 sup 2 Ce and sup 1 sup 3 sup 1 La, produced in the sup 3 sup 7 Cl + sup 1 sup 0 sup 0 Mo reaction. The results appear to be configuration dependent and, for sup 1 sup 3 sup 3 Pr and sup 1 sup 3 sup 2 Ce, the involvement of OMEGA=1/2 nu h sub 9 sub / sub 2 and nu f sub 7 sub / sub 2 intruder orbitals appears to enhance the collectivity at high spin (I>25 Planck constant).

  15. Magneto-structural correlations in self-assembled spin-transition nano-architectures of the [Fe{sub 4}{sup II}L{sub 4}]{sup n+} [2x2]-grid-type

    Energy Technology Data Exchange (ETDEWEB)

    Ruben, M. E-mail: mario.ruben@int.fzk.de; Breuning, E.; Lehn, J.-M.; Ksenofontov, V.; Guetlich, P.; Vaughan, G

    2004-05-01

    The magnetism of a series of tetranuclear complexes of the [Fe{sup II}{sub 4}L{sub 4}](BF{sub 4}){sub 8} [2x2]-grid-type was investigated, revealing the occurrence of spin-transition (ST) behavior within this class of compounds. The phenomenon depends directly on the nature of the substituent R{sup 1} of the ligand L. All Fe{sup II} ions in compounds with R{sup 1} substituents favoring strong ligand fields (R{sup 1}=H; OH) remain completely in the diamagnetic low-spin state. Only the complex bearing R{sup 1}=Ph exhibits thermally induced ST behavior.

  16. Ionic changes in the mitotic apparatus at the metaphase/anaphase transition

    OpenAIRE

    1983-01-01

    We have employed a series of permeant, nontoxic, fluorescent probes to detect changes in ionic conditions within the mitotic apparatus of living endosperm cells of Haemanthus during the transition from metaphase to anaphase. Fluorescence emission intensity measurements from the spindle for chlorotetracycline (CTC) decline before the onset of anaphase, indicating a reduction in the amount of membrane- associated Ca2+ and suggesting an efflux of Ca2+ from membrane compartments into the spindle....

  17. Changes in Drinking Patterns Across the Transition to College Among First-Year College Males

    OpenAIRE

    LaBrie, Joseph; LAMB, TOBY; PEDERSEN, ERIC

    2008-01-01

    Few studies examine changes in drinking behavior during the transition from high school to college. Using a sample of 239 first-year males, we hypothesized that participants would increase drinking from pre-college to the first month of college. Results reveal a general trend toward increased drinking upon entering college. Caucasians increased drinking more than non-Caucasians. Social expectancies of alcohol moderated increases in drinking behavior. These findings indicate that differential ...

  18. A tool to evaluate local biophysical effects on temperature due to land cover change transitions

    Science.gov (United States)

    Perugini, Lucia; Caporaso, Luca; Duveiller, Gregory; Cescatti, Alessandro; Abad-Viñas, Raul; Grassi, Giacomo; Quesada, Benjamin

    2017-04-01

    Land Cover Changes (LCC) affect local, regional and global climate through biophysical variations of the surface energy budget mediated by albedo, evapotranspiration, and roughness. Assessment of the full climate impacts of anthropogenic LCC are incomplete without considering biophysical effects, but the high level of uncertainties in quantifying their impacts to date have made it impractical to offer clear advice on which policy makers could act. To overcome this barrier, we provide a tool to evaluate the biophysical impact of a matrix of land cover transitions, following a tiered methodological approach similar to the one provided by the IPCC to estimate the biogeochemical effects, i.e. through three levels of methodological complexity, from Tier 1 (i.e. default method and factors) to Tier 3 (i.e. specific methods and factors). In particular, the tool provides guidance for quantitative assessment of changes in temperature following a land cover transition. The tool focuses on temperature for two main reasons (i) it is the main variable of interest for policy makers at local and regional level, and (ii) temperature is able to summarize the impact of radiative and non-radiative processes following LULCC. The potential changes in annual air temperature that can be expected from various land cover transitions are derived from a dedicated dataset constructed by the JRC in the framework of the LUC4C FP7 project. The inputs for the dataset are air temperature values derived from satellite Earth Observation data (MODIS) and land cover characterization from the ESA Climate Change Initiative product reclassified into their IPCC land use category equivalent. This data, originally at 0.05 degree of spatial resolution, is aggregated and analysed at regional level to provide guidance on the expected temperature impact following specific LCC transitions.

  19. Arthritis-related work transitions: a prospective analysis of reported productivity losses, work changes, and leaving the labor force.

    Science.gov (United States)

    Gignac, Monique A M; Cao, Xingshan; Lacaille, Diane; Anis, Aslam H; Badley, Elizabeth M

    2008-12-15

    To prospectively examine arthritis-related productivity losses, work changes, and leaving employment, the relationships among these work transitions, and the factors associated with them. Participants with inflammatory arthritis or osteoarthritis were interviewed at 4 time points, 18 months apart, using a structured questionnaire. At baseline (T1), all participants (n = 490; 381 women, 109 men) were employed. At T2, T3, and T4, the sample decreased to 413, 372, and 349 participants, respectively. Respondents were recruited using community advertising and from rheumatology and rehabilitation clinics. Work transitions considered were productivity losses (absenteeism, job disruptions), work changes (reduced hours, changing jobs), and leaving employment. Also measured were demographic, illness, work context, and psychological variables. Generalized estimation equations modeled predictors of work transitions over time. Although 63.1% of respondents remained employed throughout the study, work transitions were common (reported by 76.5% of participants). Productivity losses, especially job disruptions such as being unable to take on extra work, were the most frequently reported. Work transitions were related to subsequently making other work transitions, including leaving employment. Age, sex, education, activity limitations, control, depression, and arthritis-work spillover were also associated with work transitions. This study sheds light on a process of diverse employment changes that may occur in the lives of many individuals with arthritis. It emphasizes the interrelationships among work transitions, as well as other factors in predicting work transitions, and it provides insight into work changes that may signal impending difficulties with remaining employed.

  20. Solvation dynamics monitored by combined X-ray spectroscopies and scattering: photoinduced spin transition in aqueous [Fe(bpy)3]2+

    DEFF Research Database (Denmark)

    Bressler, C.; Gawelda, W.; Galler, A.

    2014-01-01

    We have studied the photoinduced low spin (LS) to high spin (HS) conversion of aqueous Fe(bpy)3 with pulse-limited time resolution. In a combined setup permitting simultaneous X-ray diffuse scattering (XDS) and spectroscopic measurements at a MHz repetition rate we have unraveled the interplay be...... the number of free parameters in the XDS analysis, and both combined permit extraction of information about the structural dynamics of the first solvation shell....

  1. Changes in physical activity and sedentary behavior during the transition from elementary to secondary school.

    Science.gov (United States)

    Rutten, Cindy; Boen, Filip; Seghers, Jan

    2014-11-01

    The purpose of this study was to identify longitudinal changes in physical activity (PA) and sedentary behavior (SB) and to analyze its association with gender and weight status during the transition from elementary to secondary school. Flemish children were recruited in 6th grade of elementary school (age = 10.97 ± 0.41) and reassessed 2 years later (age = 12.96 ± .40). Children completed a questionnaire on moderate to vigorous PA and SB and wore pedometers to monitor habitual PA. Longitudinal data from 472 children were analyzed. A significant decrease was observed in self-reported moderate to vigorous PA (-12.2%), but not in pedometer-determined PA. With respect to SB, a pronounced increase in recreational computer use was found (+3.22 hours/week), particularly in overweight boys (+8.18 hours/week). Finally, a significant increase in time spent on homework was observed in girls (+3.57 hours/week) and normal weight children (+2.83 hours/week). No longitudinal change in pedometer-determined PA was observed. Nevertheless, the decline in self-reported moderate-to-vigorous PA suggests that the transition to secondary school induced a change in the contribution of different types of PA. Finally, time spent on homework and recreational computer use increased during the school transition.

  2. Spin Superfluidity in Biaxial Antiferromagnetic Insulators

    Science.gov (United States)

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

    2017-03-01

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

  3. Creating organizational innovations in countries in transition using Finnish change laboratory: A case study from Serbia

    Directory of Open Access Journals (Sweden)

    Bodrožić Zlatko

    2012-01-01

    Full Text Available The Finnish Change Laboratory intervention method has been used in several Western countries to support innovation and learning within organizations. This study explored the applicability of the Change Laboratory method to work activities in Eastern European transition economies. The case of a Change Laboratory project at a Serbian publishing house was examined and discussed. The Change Laboratory led to a clear break from previous models and resulted in a new, much more efficient model of work organization based on teams. The studied publishing house can be characterized as an innovator within a relatively laggard industry. This characteristic increased the Serbian publisher’s potential for developing “learning partnerships” with publishing activities in EU Member States. These “learning partnerships” enabled appropriate Western concepts to be found that could be used as stimuli to develop a new model of work for the publishing house during the Change Laboratory.

  4. Many-Body Mobility Edge in a Mean-Field Quantum Spin Glass

    Science.gov (United States)

    Laumann, C. R.; Pal, A.; Scardicchio, A.

    2014-11-01

    The quantum random energy model provides a mean-field description of the equilibrium spin glass transition. We show that it further exhibits a many-body localization-delocalization (MBLD) transition when viewed as a closed quantum system. The mean-field structure of the model allows an analytically tractable description of the MBLD transition using the forward-scattering approximation and replica techniques. The predictions are in good agreement with the numerics. The MBLD transition lies at energy density significantly above the equilibrium spin glass transition, indicating that the closed system dynamics freezes well outside of the traditional glass phase. We also observe that the structure of the eigenstates at the MBLD critical point changes continuously with the energy density, raising the possibility of a family of critical theories for the MBLD transition.

  5. Radical change in healthcare organization: mapping transition between templates, enabling factors, and implementation processes.

    Science.gov (United States)

    Chreim, Samia; Williams, B E; Coller, Kristene E

    2012-01-01

    The purpose of this paper is to examine: the content of radical change by mapping differences between two templates for organizing delivery of healthcare; the enabling and constraining mechanisms underlying major change from one template to another; and the processes implicated in change implementation. Longitudinal, qualitative case study design allowed the tracking, over a four-year period, of the transformation of healthcare service in a community from provider-centered, fragmented delivery to patient-centered, integrated delivery. The authors conducted 90 interviews at three intervals, observed meetings, and analyzed internal and external documents. Concepts on content, process and mechanisms were used to analyze the data. Transition from one template to another involves radical change in structures/systems and underlying values. Mechanisms precipitating and enabling change include: powerful stakeholders' dissatisfaction with current template and commitment to a new one, willingness to resource the change, provision of credible leadership, and manipulation of incentive programs. Radical change is underlain by a series of micro change processes that involve emergent, non-linear dynamics, and that follow their own track with enabling and constraining mechanisms. The paper describes a case of positive, successful change. Implications include importance of: attention to power dynamics, persistent leadership, elimination of boundaries between collaborating groups, and aligning incentives with desired practice changes; and attending to both variance and process in understanding healthcare change.

  6. Deformed Fredkin spin chain with extensive entanglement

    Science.gov (United States)

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

    2017-06-01

    We introduce a new spin chain which is a deformation of the Fredkin spin chain and has a phase transition between bounded and extensive entanglement entropy scaling. In this chain, spins have a local interaction of three nearest neighbors. The Hamiltonian is frustration-free and its ground state can be described analytically as a weighted superposition of Dyck paths that depends on a deformation parameter t. In the purely spin 1/2 case, whenever t\

  7. Vaporization of Kitaev spin liquids.

    Science.gov (United States)

    Nasu, Joji; Udagawa, Masafumi; Motome, Yukitoshi

    2014-11-07

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

  8. Spin-mixing in noncollinear ferromagnetic metals as basis of femtosecond magnetization dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Steiauf, Daniel; Faehnle, Manfred [Max-Planck-Institut fuer Metallforschung, Stuttgart (Germany)

    2008-07-01

    A simple phenomenological model for the ultrafast demagnetization of a system after laser pulse irradiation is presented. The basic ideas are very similar to those of the Elliott-Yafet mechanism. If the spinor-field wavefunctions of the electrons are mixtures of spin-up and spin-down states depending on the wave vector, the transitions between states with different wave vectors due to scattering at defects or phonons change the spin polarization of the electrons, whereby angular momentum is transferred to the lattice via spin-orbit coupling. In collinear magnetic configurations the spin-mixing arises exclusively from spin-orbit coupling and thus it is very small, requiring very many scattering events for a considerable change of the magnetic moment of the system. In noncollinear magnetic systems there is an additional and much stronger spin-mixing arising from the much larger exchange couplings. For systems like Ni which are ferromagnetic in the ground state a noncollinearity arises at nonzero temperatures due to thermal disordering. The degree of spin-mixing due to spin-orbit coupling on the one hand and due to the noncollinearity on the other hand is calculated quantitatively by the ab-initio density functional electron theory.

  9. Universal spin dynamics in quantum wires

    Science.gov (United States)

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

    2017-10-01

    We discuss the universal spin dynamics in quasi-one-dimensional systems including the real spin in narrow-gap semiconductors like InAs and InSb, the valley pseudospin in staggered single-layer graphene, and the combination of real spin and valley pseudospin characterizing single-layer transition metal dichalcogenides (TMDCs) such as MoS2, WS2, MoS2, and WSe2. All these systems can be described by the same Dirac-like Hamiltonian. Spin-dependent observable effects in one of these systems thus have counterparts in each of the other systems. Effects discussed in more detail include equilibrium spin currents, current-induced spin polarization (Edelstein effect), and spin currents generated via adiabatic spin pumping. Our work also suggests that a long-debated spin-dependent correction to the position operator in single-band models should be absent.

  10. Youth transitioning out of foster care: an evaluation of a Supplemental Security Income policy change.

    Science.gov (United States)

    King, Laura; Rukh-Kamaa, Aneer

    2013-01-01

    Youths with disabilities face numerous challenges when they transition to adulthood. Those who are aging out of foster care face the additional challenge of losing their foster care benefits, although some will be eligible for Supplemental Security Income (SSI) payments after foster care ceases. However, the time needed to process SSI applications exposes those youths to a potential gap in the receipt of benefits as they move between foster care and SSI. We evaluate the effects of a 2010 Social Security Administration policy change that allows such youths to apply for SSI payments 60 days earlier than the previous policy allowed. The change provides additional time for processing claims before the applicant ages out of the foster care system. We examine administrative records on SSI applications from before and after the policy change to determine if the change has decreased the gap between benefits for the target population.

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

    Science.gov (United States)

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

    2018-01-01

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

  12. Metal-insulator transition in Nd{sub 1−x}Eu{sub x}NiO{sub 3}: Entropy change and electronic delocalization

    Energy Technology Data Exchange (ETDEWEB)

    Jardim, R. F., E-mail: rjardim@if.usp.br; Andrade, S. [Instituto de Física, Universidade de São Paulo, CP 66318, São Paulo 05315-970 (Brazil); Barbeta, V. B. [Departamento de Física, Centro Universitário da FEI, São Bernardo do Campo 09850-901 (Brazil); Escote, M. T. [Centro de Engenharia, Modelagem e Ciências Sociais Aplicadas, Universidade Federal do ABC, Santo André 09210-170 (Brazil); Cordero, F. [CNR-ISC, Istituto dei Sistemi Complessi, Area della Ricerca di Roma - Tor Vergata, Via del Fosso del Cavaliere 100, I-00133 Rome (Italy); Torikachvili, M. S. [Department of Physics, San Diego State University, San Diego, California 92182-1233 (United States)

    2015-05-07

    The metal-insulator (MI) phase transition in Nd{sub 1–x}Eu{sub x}NiO{sub 3}, 0 ≤ x ≤ 0.35, has been investigated through the pressure dependence of the electrical resistivity ρ(P, T) and measurements of specific heat C{sub P}(T). The MI transition temperature (T{sub MI}) increases with increasing Eu substitution and decreases with increasing pressure. Two distinct regions for the Eu dependence of dT{sub MI}/dP were found: (i) for x ≤ 0.15, dT{sub MI}/dP is nearly constant and ∼−4.3 K/kbar; (ii) for x ≥ 0.15, dT{sub MI}/dP increases with x and it seems to reach a saturation value ∼−6.2 K/kbar for the x = 0.35 sample. This change is accompanied with a strong decrease in the thermal hysteresis in ρ(P, T) between the cooling and warming cycles, observed in the vicinity of T{sub MI}. The entropy change (ΔS) at T{sub MI} for the sample x = 0, estimated by using the dT{sub MI}/dP data and the Clausius-Clapeyron equation, resulted in ΔS ∼ 1.2 J/mol K, a value in line with specific heat measurements. When the Eu concentration is increased, the antiferromagnetic (AF) and the MI transitions are separated in temperature, permitting that an estimate of the entropy change due to the AF/Paramagnetic transition be carried out, yielding ΔS{sub M} ∼ 200 mJ/mol K. This value is much smaller than that expected for a s = 1/2 spin system. The analysis of ρ(P, T) and C{sub P}(T) data indicates that the entropy change at T{sub MI} is mainly due to the electronic delocalization and not related to the AF transition.

  13. Spin clustering of accreting X-ray neutron stars as possible evidence of quark matter

    Energy Technology Data Exchange (ETDEWEB)

    Glendenning, Norman K.; Weber, Fridolin

    2001-06-27

    A neutron star in binary orbit with a low-mass non-degenerate companion becomes a source of x-rays with millisecond variability when mass accretion spins it up. Centrifugally driven changes in density profile may initiate a phase transition in a growing region of the core parallel to what may take place in an isolated millisecond pulsar, but in reverse. Such a star will spend a longer time in the spin frequency range over which the transition occurs than elsewhere because the change of phase, paced by the spinup rate, is accompanied by a growth in the moment of inertia. The population of accreters will exhibit a clustering in the critical frequency range. A phase change triggered by changing spin and the accompanying adjustment of moment of inertia has its analogue in rotating nuclei.

  14. Calculated Changes in the Elastic Properties of MgCNi3 at the Superconducting Transition

    Directory of Open Access Journals (Sweden)

    R. Abd-Shukor

    2013-01-01

    Full Text Available We calculated the elastic properties of MgCNi3 at the superconducting transition ( using various thermodynamic and acoustic data. From the calculations, a step discontinuity of 8 ppm in the bulk modulus, 7 ppm in the Young’s modulus, and 3 ppm in the longitudinal sound velocity ( is expected at . The step discontinuities at the transition temperature indicated the importance of lattice changes to the superconducting mechanism of MgCNi3. The Debye temperature was calculated to be 460 K. The electron-phonon coupling constants calculated in the weak and strong coupling limits of the BCS theory and the van Hove scenario showed that MgCNi3 is a moderately strong coupled superconductor.

  15. Changes in Sports Participation across Transition to Retirement: Modification by Migration Background and Acculturation Status

    Directory of Open Access Journals (Sweden)

    Johanna-Katharina Schönbach

    2017-11-01

    Full Text Available While total physical activity decreases over the life course, sports and leisure-time physical activity (LTPA have shown to increase after transition to retirement. This paper aimed to investigate whether this change in sports participation differs (1 between non-migrant persons (NMP versus persons with a migrant background (PMB, and (2 by acculturation status. Data was drawn from 16 waves of the German Socio-Economic Panel Study (SOEP including 2664 NMP and 569 PMB. PMB were grouped according to acculturation status (integrated, assimilated, marginalised, separated, assessed regarding three dimensions (language, social interaction and identification. We applied multilevel logistic regression models, adjusting for sex, retirement age, socioeconomic status, health status and body mass index. Our results show that (1 transition to retirement led to an increase in the sports participation of NMP during the first 5 years and the subsequent 5 years after retirement. Changes in sports participation were modified by migration status: In PMB sports participation increased to a lesser extent than in NMP. (2 While sports participation of integrated PMB was not significantly different from NMP in the preretirement phase, sports participation among integrated PMB increased less after retirement compared with NMP. Marginalized and assimilated PMB did not show consistent sports participation patterns before retirement, but seemingly increased their sports participation less than NMP over the retirement transition. Separated PMB had particularly low levels of sports participation. Considering that LTPA is a key factor for healthy ageing, the increasing gap in levels of sports participation after transition to retirement indicates the need for interventions targeting physical activity of the older migrant population.

  16. The timing of molecular and morphological changes underlying reproductive transitions in wild tomatoes (Solanum sect. Lycopersicon).

    Science.gov (United States)

    Vosters, S L; Jewell, C P; Sherman, N A; Einterz, F; Blackman, B K; Moyle, L C

    2014-04-01

    Molecular mechanisms underlying the transition from genetic self-incompatibility to self-compatibility are well documented, but the evolution of other reproductive trait changes that accompany shifts in reproductive strategy (mating system) remains comparatively under-investigated. A notable exception is the transition from exserted styles to styles with recessed positions relative to the anthers in wild tomatoes (Solanum Section Lycopersicon). This phenotypic change has been previously attributed to a specific mutation in the promoter of a gene that influences style length (style2.1); however, whether this specific regulatory mutation arose concurrently with the transition from long to short styles, and whether it is causally responsible for this phenotypic transition, has been poorly investigated across this group. To address this gap, we assessed 74 accessions (populations) from 13 species for quantitative genetic variation in floral and reproductive traits as well as the presence/absence of deletions at two different locations (StyleD1 and StyleD2) within the regulatory region upstream of style2.1. We confirmed that the putatively causal deletion variant (a 450-bp deletion at StyleD1) arose within self-compatible lineages. However, the variation and history of both StyleD1 and StyleD2 was more complex than previously inferred. In particular, although StyleD1 was statistically associated with differences in style length and stigma exsertion across all species, we found no evidence for this association within two species polymorphic for the StyleD1 mutation. We conclude that the previous association detected between phenotypic and molecular differences is most likely due to a phylogenetic association rather than a causal mechanistic relationship. Phenotypic variation in style length must therefore be due to other unexamined linked variants in the style2.1 regulatory region. © 2014 John Wiley & Sons Ltd.

  17. Changes in Sports Participation across Transition to Retirement: Modification by Migration Background and Acculturation Status.

    Science.gov (United States)

    Schönbach, Johanna-Katharina; Pfinder, Manuela; Börnhorst, Claudia; Zeeb, Hajo; Brand, Tilman

    2017-11-08

    While total physical activity decreases over the life course, sports and leisure-time physical activity (LTPA) have shown to increase after transition to retirement. This paper aimed to investigate whether this change in sports participation differs (1) between non-migrant persons (NMP) versus persons with a migrant background (PMB), and (2) by acculturation status. Data was drawn from 16 waves of the German Socio-Economic Panel Study (SOEP) including 2664 NMP and 569 PMB. PMB were grouped according to acculturation status (integrated, assimilated, marginalised, separated), assessed regarding three dimensions (language, social interaction and identification). We applied multilevel logistic regression models, adjusting for sex, retirement age, socioeconomic status, health status and body mass index. Our results show that (1) transition to retirement led to an increase in the sports participation of NMP during the first 5 years and the subsequent 5 years after retirement. Changes in sports participation were modified by migration status: In PMB sports participation increased to a lesser extent than in NMP. (2) While sports participation of integrated PMB was not significantly different from NMP in the preretirement phase, sports participation among integrated PMB increased less after retirement compared with NMP. Marginalized and assimilated PMB did not show consistent sports participation patterns before retirement, but seemingly increased their sports participation less than NMP over the retirement transition. Separated PMB had particularly low levels of sports participation. Considering that LTPA is a key factor for healthy ageing, the increasing gap in levels of sports participation after transition to retirement indicates the need for interventions targeting physical activity of the older migrant population.

  18. Entanglement in the quantum one-dimensional integer spin S Heisenberg antiferromagnet

    Science.gov (United States)

    Lima, L. S.

    2017-10-01

    We use the modified spin wave theory of Takahashi to study the entanglement entropy in the quantum one-dimensional integer spin Heisenberg antiferromagnet. We calculate the entanglement entropy of this spin system that is well known to be a quantum wire, in the classical limit (N → ∞). We obtain a decreasing the entanglement entropy with the temperature and we obtain none change in the entanglement in the point Δ = 1 at T = 0 where the system presents a quantum phase transition from a gapless phase in the spectrum Δ < 1 to a gapped phase Δ ≥ 1.

  19. Spin current

    CERN Document Server

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

    2017-01-01

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

  20. Matrix-assisted relaxation in Fe(phen){sub 2}(NCS){sub 2} spin-crossover microparticles, experimental and theoretical investigations

    Energy Technology Data Exchange (ETDEWEB)

    Enachescu, Cristian, E-mail: cristian.enachescu@uaic.ro; Stancu, Alexandru [Faculty of Physics, “Alexandru Ioan Cuza” University, 700506 Iasi (Romania); Tanasa, Radu [Faculty of Physics, “Alexandru Ioan Cuza” University, 700506 Iasi (Romania); Department of Engineering, University of Cambridge, CB2 1PZ Cambridge (United Kingdom); Tissot, Antoine [Institut de Chimie Moléculaire et des Matériaux d' Orsay, Université Paris Sud, Université Paris-Saclay, CNRS, 91405 Orsay (France); Institut Lavoisier de Versailles, UMR 8180, CNRS, Université de Versailles-Saint Quentin en Yvelines, 78035 Versailles (France); Laisney, Jérôme; Boillot, Marie-Laure, E-mail: marie-laure.boillot@u-psud.fr [Institut de Chimie Moléculaire et des Matériaux d' Orsay, Université Paris Sud, Université Paris-Saclay, CNRS, 91405 Orsay (France)

    2016-07-18

    In this study, we present the influence of the embedding matrix on the relaxation of Fe(phen){sub 2}(NCS){sub 2} (phen = 1,10-phenanthroline) spin-transition microparticles as revealed by experiments and provide an explanation within the framework of an elastic model based on a Monte-Carlo method. Experiments show that the shape of the high-spin → low-spin relaxation curves is drastically changed when the particles are dispersed in glycerol. This effect was considered in the model by means of interactions between the microparticles and the matrix. A faster start of the relaxation for microparticles embedded in glycerol is due to an initial positive local pressure acting on the edge spin-crossover molecules from the matrix side. This local pressure diminishes and eventually becomes negative during relaxation, as an effect of the decrease of the volume of spin-crossover microparticles from high-spin to low-spin.

  1. 76 FR 18930 - Medicare Programs: Changes to the End-Stage Renal Disease Prospective Payment System Transition...

    Science.gov (United States)

    2011-04-06

    ...: Changes to the End-Stage Renal Disease Prospective Payment System Transition Budget-Neutrality Adjustment... period. SUMMARY: This interim final rule with comment will revise the end-stage renal disease (ESRD) transition budget-neutrality adjustment finalized in the CY 2011 ESRD Prospective Payment System (PPS) final...

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

    OpenAIRE

    Shen, Yelong; Zhao, Bin; Yan, Lirong; Jann, Kay; Wang, Guangbin; Wang, Junli; Wang, Bao; Pfeuffer, Josef; Qian, Tianyi; Wang, Danny J. J.

    2017-01-01

    Diabetes has been reported to affect the microvasculature and lead to cerebral small vessel disease (SVD). Past studies using arterial spin labeling (ASL) at single post-labeling delay reported reduced cerebral blood flow (CBF) in patients with type 2 diabetes. The purpose of this study was to characterize cerebral hemodynamic changes of type 2 diabetes using a multi-inversion-time 3D GRASE pulsed ASL (PASL) sequence to simultaneously measure CBF and bolus arrival time (BAT). Thirty-six patie...

  3. Spin multiplicities

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-02-05

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

  4. Dietary transition, nutritional and health outcomes, and changing agrifood production and trade patterns

    DEFF Research Database (Denmark)

    Yu, Wusheng; Jensen, Hans Grinsted; Cao, Lijuan

    and health outcomes of diet transition and alternative diets on the one hand and the associated agricultural and food production and trade effects on the other hand, using the Chinese case as an example. We base this analysis in a modified GTAP model featuring the demand, production and supply and trade...... such as those from the WHO and the Chinese health authority, as exogenous changes to consumer demands via shifts of consumer preferences. Simulations of these scenarios will then reveal the production and trade pattern changes that are necessary to accommodate the demand shifts, as well as the associated...... efficiency and welfare consequences. Realizing that changing dietary trends are likely to be costly, in a more refined scenario, we consider public policy options to influence consumer choices for purposes of reaching a given alternative diet target. Since the costs of the policy intervention...

  5. Magnetic property change in Kondo impurity-to-Kondo lattice transition in Cesub(x)Lasub(1-x)Cusub(2)Sisub(2) series

    Energy Technology Data Exchange (ETDEWEB)

    Aliev, F.G.; Brandt, N.B.; Moshchalkov, V.V.; Lutsiv, R.V.; Chudinov, S.M. (Moskovskij Gosudarstvennyj Univ. (USSR))

    1983-08-01

    Magnetic properties of isostructural substitution solid solutions of Cesub(x)Lasub(1-x)Cusub(2)Sisub(2) (0 < x <= 1) were investigated in 0.06 <= T <= 2.5 K range. The break, related to Cesub(x)Lasub(1-x)Cusub(2)Sisub(2) transition to spin glass, was revealed on the temperature dependence of the magnetic susceptibility at T=Tsub(SG). It was found that Tsub(SG) initially (0.2 <= x <= 0.6) grows from Tsub(SG)=0.3 K up to Tsub(SG)=1.6 K, and then Tsub(SG) value decreases in x > or approximately 0.8 range and Cesub(x)Lasub(1-x)Cusub(2)Sisub(2) compounds become superconducting near x approximately 1. Such change of magnetic properties of Cesub(x)Lasub(1-x)Cusub(2)Sisub(2) relates with transition from the kondo-impurity (x <<< 1) to in the kondo-lattice (x approximately 1) and formation of narrow resonance in proximity to the Fermi energy at x ..-->.. 1, which determines the decrease of the effective magnetic moment of Ce ions (and Tsub(SG) decrease in x > or approximately 0.8 range) and appearance of superconductivity of heavy fermions in CeCu/sub 2/Si/sub 2/.

  6. [Change of awareness level of the Japanese Food Guide Spinning Top and relation with sociodemographic and health-related characteristics].

    Science.gov (United States)

    Takaizumi, Kanae; Harada, Kazuhiro; Nakamura, Yoshio

    2011-11-01

    The purpose of this study was to examine the sociodemographic and health-related characteristics of those who are unaware of the Japanese Food Guide Spinning Top (Food Guide). A longitudinal study was conducted using an Internet-based questionnaire with 1,012 Japanese adults (40.2 +/- 10.0 years, mean +/- SD) recruited from registrants of a Japanese social research company. Conducted between November 2007 (T1) and December 2008 (T2), the survey included items on awareness level ("I know the contents." "I have heard of this Guide." or "I have not heard of this Guide.") of the Food Guide as the dependent variable, and demographics factors (e.g., age, education status, marital status, household income, and employment status) and health-related characteristics (obesity, abdominal obesity, and insufficient physical activity) as the independent variables. Multivariate logistic regression analysis was used to analyze the relation between awareness level and each variable. The relation between change of awareness level (T1-T2) and each variable was analyzed using a chi-square test. All the analyses were stratified by gender. In the multivariate logistic regression analysis adjusted for all variables, men with a household income of 5,000,000-10,000,000 yen (OR=1.78; 95% CI=1.10-2.88) were positively associated with awareness level ("I have heard of this Guide."). In contrast, unmarried women were negatively associated with awareness level in T1 ("I know the contents"; OR=0.35; 95% CI=0.17-0.70. "I have heard of this Guide"; OR=0.50; 95% CI=0.27-0.92). In men, the awareness level of the Food Guide increased from T1 to T2, change of awareness level (T1; "I have not heard of this Guide") and education status being related (P=0.023). In women, the awareness levels overall did not improve from T1 to T2, but change of awareness level (T1; "I have heard of this Guide") was associated with household income (Plevel was not associated with health-related characteristics. The results

  7. Ionic changes in the mitotic apparatus at the metaphase/anaphase transition

    Science.gov (United States)

    1983-01-01

    We have employed a series of permeant, nontoxic, fluorescent probes to detect changes in ionic conditions within the mitotic apparatus of living endosperm cells of Haemanthus during the transition from metaphase to anaphase. Fluorescence emission intensity measurements from the spindle for chlorotetracycline (CTC) decline before the onset of anaphase, indicating a reduction in the amount of membrane- associated Ca2+ and suggesting an efflux of Ca2+ from membrane compartments into the spindle. Subsequent to the onset of anaphase, we observe increases in fluorescence with both 8-anilino-1-naphthalene sulfonate (ANS) and 3,3'-dipentyl 2,2'-dioxacarbocyanine (diO-C5(3)), sensitive to cationic and anionic charges at membrane surfaces, respectively. The increases with ANS and diO-C5(3) suggest that redistributions of ions within the spindle accompany anaphase motion. During the metaphase/anaphase transition, spindle membrane content remains constant, as evidenced by unchanging fluorescence with the hydrophobic probe, N-phenyl-1-naphthylamine (NPN). Shifts in emission intensity from the nonspindle cytoplasm or from the spindle poles do not accompany the changes in fluorescence we observe in the spindle, suggesting that any ionic fluxes responsible for the changes in fluorescence are restricted to the spindle domain. PMID:6833373

  8. Anticipatory guidance as a principle of faculty development: managing transition and change.

    Science.gov (United States)

    Schor, Nina F; Guillet, Ronnie; McAnarney, Elizabeth R

    2011-10-01

    Although one cannot anticipate every individual's unique responses to the transitions and changes that regularly occur in academic medicine, a department-wide faculty development program, based on predictable transition points and supporting faculty at all levels, can minimize such negative responses to change as stress and burnout. In 2007, the authors implemented a new, formal faculty development program in the pediatrics department built on the principle of anticipatory guidance, defined as providing guidance in anticipation of future academic events. The primary components of the program are mentoring committees for individual junior faculty, group leadership development and teaching forums for midlevel faculty, and events that focus on life and career changes for senior faculty. Other department-wide activities augment the program, including review of grant submissions, annual review by a senior faculty committee of the progress of National Institutes of Health mentored research (K-) awardees, women faculty luncheons, and discussions about faculty development at regular faculty meetings. The department's faculty also participate in the University of Rochester Medical Center's active faculty development program. Feedback on the faculty development program has been constructive and mainly positive and will serve to guide the continuing evolution of the program.

  9. Microbial community changes in methanogenic granules during the transition from mesophilic to thermophilic conditions.

    Science.gov (United States)

    Zhu, Xinyu; Kougias, Panagiotis G; Treu, Laura; Campanaro, Stefano; Angelidaki, Irini

    2017-02-01

    Upflow anaerobic sludge blanket (UASB) reactor is one of the most applied technologies for various high-strength wastewater treatments. The present study analysed the microbial community changes in UASB granules during the transition from mesophilic to thermophilic conditions. Dynamicity of microbial community in granules was analysed using high-throughput sequencing of 16S ribosomal RNA gene amplicons, and the results showed that the temperature strictly determines the diversity of the microbial consortium. It was demonstrated that most of the microbes which were present in the initial mesophilic community were not found in the granules after the transition to thermophilic conditions. More specifically, only members from family Anaerolinaceae managed to tolerate the temperature change and contributed in maintaining the physical integrity of granular structure. On the contrary, new hydrolytic and fermentative bacteria were quickly replacing the old members in the community. A direct result from this abrupt change in the microbial diversity was the accumulation of volatile fatty acids and the concomitant pH drop in the reactor inhibiting the overall anaerobic digestion process. Nevertheless, by maintaining deliberately the pH levels at values higher than 6.5, a methanogen belonging to Methanoculleus genus emerged in the community enhancing the methane production.

  10. Changes in perceived social support and socioemotional adjustment across the elementary to junior high school transition.

    Science.gov (United States)

    Martínez, Rebecca S; Aricak, O Tolga; Graves, Misha N; Peters-Myszak, Jessica; Nellis, Leah

    2011-05-01

    One of the most fundamental factors related to psychological well being across the lifespan is whether a person perceives social support from important others in his or her life. The current study explored changes in and relationships among perceived social support (SS) and socioemotional adjustment (SEA) across the 1-year transition from elementary to junior high school. Two cohorts of students (N = 140) participated in the current study that took place across a 3-year time span. Analyses of the transition data for boys and girls together reveal declines in perceived total support and teacher support as well as an increase in self-reported school problems. When considering the sexes separately, girls' perceived total support, close friend support and school support declined while boy's self-reported school problems increased across the transition. Although social support did not emerge as a mediator or predictor for any of the socioemotional variables in the current study, results reveal that, in general, perceived social support and socioemotional functioning at the end of the last year of elementary school predicts perceived social support and socioemotional functioning at the end of the first year of junior high school. Study limitations and implications for research and practice are discussed.

  11. Frustrated mixed spin-1/2 and spin-1 Ising ferrimagnets on a triangular lattice.

    Science.gov (United States)

    Žukovič, M; Bobák, A

    2015-05-01

    Mixed spin-1/2 and spin-1 Ising ferrimagnets on a triangular lattice with sublattices A, B, and C are studied for two spin-value distributions (S(A),S(B),S(C))=(1/2,1/2,1) and (1/2,1,1) by Monte Carlo simulations. The nonbipartite character of the lattice induces geometrical frustration in both systems, which leads to the critical behavior rather different from their ferromagnetic counterparts. We confirm second-order phase transitions belonging to the standard Ising universality class occurring at higher temperatures, however, in both models these change at tricritical points (TCP) to first-order transitions at lower temperatures. In the model (1/2,1/2,1), TCP occurs on the boundary between paramagnetic and ferrimagnetic (±1/2,±1/2,∓1) phases. The boundary between two ferrimagnetic phases (±1/2,±1/2,∓1) and (±1/2,∓1/2,0) at lower temperatures is always first order and it is joined by a line of second-order phase transitions between the paramagnetic and the ferrimagnetic (±1/2,∓1/2,0) phases at a critical endpoint. The tricritical behavior is also confirmed in the model (1/2,1,1) on the boundary between the paramagnetic and ferrimagnetic (0,±1,∓1) phases.

  12. Magnetic transitions and spin-glass reentrance in two-dimensional [MnII(TCNE)(NCMe)2]X (X = PF6,AsF6,SbF6) molecular magnets

    Science.gov (United States)

    Olson, C. S.; Heth, C. L.; Alema, F. L.; Lapidus, S. H.; Stephens, P. W.; Pokhodnya, K. I.

    2013-06-01

    The structural, spectroscopic and magnetic properties of the two-dimensional (2D) molecule-based magnets of [MnII(TCNE)(NCMe)2]X (X = PF6, AsF6, SbF6; TCNE = tetracyanoethylene, NCMe = acetonitrile) composition are reported. It is shown that the alteration of the interlayer distance by increasing the anion size has little effect on the critical magnetic ordering temperature, Tc, suggesting that it depends predominantly on the intra-plane magnetic exchange. The observed field-induced irreversibility in static magnetization, a slow decay of isothermal remanence below Tc, and the dynamic susceptibility data are in accord with a re-entrant spin-glass nature of the ground state of all materials. In contrast to the isostructural Fe-based magnets, in which strong magnetocrystalline anisotropy facilitates the finite temperature magnetic ordering with the magnetization easy axis perpendicular to the μ4-TCNE•- plane, in the studied Mn-based magnets the easy axis is canted away from the normal direction, due to a small magnetocrystalline anisotropy. The two magnetic transitions observed on cooling are assigned to the ferrimagnetic long-range ordering of the normal magnetization component followed by the re-entrant spin-glass type transition resulting from a random freezing of the in-plane magnetization component.

  13. Medical student changes in self-regulated learning during the transition to the clinical environment.

    Science.gov (United States)

    Cho, Kenneth K; Marjadi, Brahm; Langendyk, Vicki; Hu, Wendy

    2017-03-21

    Self-regulated learning (SRL), which is learners' ability to proactively select and use different strategies to reach learning goals, is associated with academic and clinical success and life-long learning. SRL does not develop automatically in the clinical environment and its development during the preclinical to clinical learning transition has not been quantitatively studied. Our study aims to fill this gap by measuring SRL in medical students during the transitional period and examining its contributing factors. Medical students were invited to complete a questionnaire at the commencement of their first clinical year (T0), and 10 weeks later (T1). The questionnaire included the Motivated Strategies for Learning Questionnaire (MSLQ) and asked about previous clinical experience. Information about the student's background, demographic characteristics and first clinical rotation were also gathered. Of 118 students invited to participate, complete paired responses were obtained from 72 medical students (response rate 61%). At T1, extrinsic goal orientation increased and was associated with gender (males were more likely to increase extrinsic goal orientation) and type of first attachment (critical care and community based attachments, compared to hospital ward based attachments). Metacognitive self-regulation decreased at T1 and was negatively associated with previous clinical experience. Measurable changes in self-regulated learning occur during the transition from preclinical learning to clinical immersion, particularly in the domains of extrinsic goal orientation and metacognitive self-regulation. Self-determination theory offers possible explanations for this finding which have practical implications and point the way to future research. In addition, interventions to promote metacognition before the clinical immersion may assist in preserving SRL during the transition and thus promote life-long learning skills in preparation for real-world practice.

  14. Changes in Service and Associated Ridership Impacts near a New Light Rail Transit Line

    National Research Council Canada - National Science Library

    Jeongwoo Lee; Marlon Boarnet; Douglas Houston; Hilary Nixon; Steven Spears

    2017-01-01

    .... One area needing evaluation is whether new, high quality transit options, such as light rail, near existing transit services increase sustainable transportation mode shares and reduce car travel...

  15. Remote sensing land-cover change in Port Elizabeth during South Africa’s democratic transition

    Directory of Open Access Journals (Sweden)

    Vincent Kakembo

    2012-05-01

    Full Text Available Urban population increase has caused significant urban landscape transformation globally. Before 1994, South Africa’s highly regulated urban growth was shaped by the restrictive Prevention of Illegal Squatters Act of 1951. After the abolishment of the act in the 1980s, the period of transition to democracy in the 1990s was characterised by an unprecedented urban population influx that caused a myriad of socio-economic and environmental challenges. These challenges have consequently compounded the need to monitor urban growth for the planning and optimisation of urban spaces. The limitations of traditional mapping methods, such as surveying and photogrammetry, in urban mapping are well documented. In the recent past, satellite remote sensing has emerged as one of the most viable urban mapping tools. Using post-classification comparisons, we sought to monitor major land use and land cover (LULC changes in the city of Port Elizabeth during South Africa’s democratic transition (1990–2000. Images for 1990, 1995 and 2000 were acquired, geo-rectified and atmospherically corrected. An iterative self-organising data analysis (ISODATA was then used to generate existing LULCs. Classes generated using ISODATA were then amalgamated to the city’s major LULCs and resultant classes were validated using aerial photographs and field visits. Results showed that ‘Built-up’ and ‘Bare surface’ LULC classes had the highest increase and decrease, respectively. There was no change in the ‘Beach or dune’ LULC, whereas ‘Green vegetation’ and ‘Water’ classes had minimal changes. This study illustrates the efficacy of remote sensing in monitoring urban change and the potential of remote sensing to aid decision-making in rapidly changing urban landscapes.

  16. The role of change management in the District Health Authority Consolidation (Transition and Design) project in Nova Scotia.

    Science.gov (United States)

    Stevenson, Colin; Burstall, Dawn

    2016-03-01

    The District Health Authority Consolidation (Transition and Design) project in Nova Scotia was initiated to consolidate the existing nine district health authorities into one provincial health authority. This article provides an overview of the internal change management approach and activities that were developed to support the various phases of the design and transition process. Three phases of work are outlined, and specific change management activities are described as are lessons learned from the overall approach. © 2016 The Canadian College of Health Leaders.

  17. Non-Abelian spin liquid in a spin-one quantum magnet.

    Science.gov (United States)

    Grover, Tarun; Senthil, T

    2011-08-12

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

  18. Thermodynamics of Chiral Spin Liquids with Abelian and Non-Abelian Anyons.

    Science.gov (United States)

    Nasu, Joji; Motome, Yukitoshi

    2015-08-21

    Thermodynamic properties of chiral spin liquids are investigated for a variant of the Kitaev model defined on a decorated honeycomb lattice. Using the quantum Monte Carlo simulation, we find that the model exhibits a finite-temperature phase transition associated with the time reversal symmetry breaking, in both topologically trivial and nontrivial regions. Numerical results for the Chern number and the thermal Hall conductivity indicate that the phase transition changes from a continuous to a discontinuous transition as we vary the coupling constants to reach the non-Abelian phase coming from the Abelian phase of the model. In addition, we find as a diagnostic of the chiral spin liquids, successive crossovers with multistage entropy release above the critical temperature, which indicates that the hierarchical fractionalization of a quantum spin occurs differently between the two regions.

  19. Variations in Academic Performance Trajectories during High School Transition: Exploring Change Profiles Via Multidimensional Scaling Growth Profile Analysis

    Science.gov (United States)

    Ding, Cody S.

    2008-01-01

    This study examines the baseline change profiles of academic performance (math and English) trajectories during the high school transition for the students who went from middle school to high school. Using multidimensional scaling growth profile analysis, we identified a no-change group plus 4 other groups with different change profile types: 1…

  20. Changes in healthy food habits after transition to old age retirement.

    Science.gov (United States)

    Helldán, Anni; Lallukka, Tea; Rahkonen, Ossi; Lahelma, Eero

    2012-08-01

    Retirement is one of the major transitions in the life course. However, it is poorly understood how health behaviours, such as food habits, might change after retirement. This study aimed to examine whether healthy food habits change after the transition to old age retirement and whether socio-demographic or health-related factors explain the association between retirement, being continuously employed and healthy food habits at follow-up. The data were derived from the Helsinki Health Study cohort on the staff of the City of Helsinki, Finland. The baseline questionnaire survey data were collected in 2000-02 and the follow-up in 2007. We included only participants who were aged 55-60 years at baseline and entered old age retirement during the follow-up (n = 1156, 76% women) or remained continuously employed (n = 1269, 79% women). Food habits from a food frequency questionnaire included eight items formed according to the Finnish and Nordic dietary recommendations. Logistic regression models were fitted to examine the associations between retirement, being continuously employed and healthy food habits at follow-up. Healthy food habits increased more among retired women than those continuously employed (P = 0.03). At follow-up retired women had healthier food habits than continuously employed women after adjusting for baseline food habits [OR = 1.36 (1.12-1.65)]. Among men, healthy food habits were unassociated with retirement. Transition to old age retirement is likely to have beneficial effects on food habits among women. This helps prevent major diseases and supports better public health among ageing people.

  1. Livestock in a changing climate: production system transitions as an adaptation strategy for agriculture

    Science.gov (United States)

    Weindl, Isabelle; Lotze-Campen, Hermann; Popp, Alexander; Müller, Christoph; Havlík, Petr; Herrero, Mario; Schmitz, Christoph; Rolinski, Susanne

    2015-09-01

    Livestock farming is the world’s largest land use sector and utilizes around 60% of the global biomass harvest. Over the coming decades, climate change will affect the natural resource base of livestock production, especially the productivity of rangeland and feed crops. Based on a comprehensive impact modeling chain, we assess implications of different climate projections for agricultural production costs and land use change and explore the effectiveness of livestock system transitions as an adaptation strategy. Simulated climate impacts on crop yields and rangeland productivity generate adaptation costs amounting to 3% of total agricultural production costs in 2045 (i.e. 145 billion US). Shifts in livestock production towards mixed crop-livestock systems represent a resource- and cost-efficient adaptation option, reducing agricultural adaptation costs to 0.3% of total production costs and simultaneously abating deforestation by about 76 million ha globally. The relatively positive climate impacts on grass yields compared with crop yields favor grazing systems inter alia in South Asia and North America. Incomplete transitions in production systems already have a strong adaptive and cost reducing effect: a 50% shift to mixed systems lowers agricultural adaptation costs to 0.8%. General responses of production costs to system transitions are robust across different global climate and crop models as well as regarding assumptions on CO2 fertilization, but simulated values show a large variation. In the face of these uncertainties, public policy support for transforming livestock production systems provides an important lever to improve agricultural resource management and lower adaptation costs, possibly even contributing to emission reduction.

  2. Spin glasses

    CERN Document Server

    Bovier, Anton

    2007-01-01

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

  3. Dynamics of phase transitions in La{sub 1-x}Sr{sub x}CoO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Louca, Despina

    2003-05-01

    The unique spin transitions present in lanthanum cobaltate subject the system to variable spin-lattice coupling and to a potentially new mechanism for the insulator-metal transition. The transitions occur with increasing temperature and carrier concentration from low spin (non-magnetic) to either a high-spin or an intermediate-spin (IS) (both magnetic) configurations where the IS state is Jahn-Teller active. Earlier studies of the local structure provided strong evidence for the presence of localized lattice distortions associated with a Jahn-Teller active mode with Sr doping. Recent measurements of the dynamic structure function couple the local effects to changes in lattice dynamics with temperature and composition and provide a time-scale for the atomic fluctuations.

  4. The argument expression of change-of-state verbs and pseudo-transitive verbs

    Directory of Open Access Journals (Sweden)

    Eva Kardos

    2010-12-01

    Full Text Available Normal 0 21 MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Normál táblázat"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman";} In this paper, I aim to explore the argument realization properties of change-of-state verbs and those of pseudo-transitives. I pursue this by (1 providing an overview of two approaches towards the representation of argument structure and event structure information and (2 applying them to English and Hungarian change-of-state verbs and pseudo-transitives. In the end, although I acknowledge the merits of both models, I would like to emphasize the descriptive power of the second model with regard to my Hungarian data.

  5. Microbial community changes in methanogenic granules during the transition from mesophilic to thermophilic conditions

    DEFF Research Database (Denmark)

    Zhu, Xinyu; Kougias, Panagiotis; Treu, Laura

    2017-01-01

    Upflow anaerobic sludge blanket (UASB) reactor is one of the most applied technologies for various high-strength wastewater treatments. The present study analysed the microbial community changes in UASB granules during the transition from mesophilic to thermophilic conditions. Dynamicity...... of microbial community in granules was analysed using high-throughput sequencing of 16S ribosomal RNA gene amplicons, and the results showed that the temperature strictly determines the diversity of the microbial consortium. It was demonstrated that most of the microbes which were present in the initial...... hydrolytic and fermentative bacteria were quickly replacing the old members in the community. A direct result from this abrupt change in the microbial diversity was the accumulation of volatile fatty acids and the concomitant pH drop in the reactor inhibiting the overall anaerobic digestion process...

  6. Spin currents in metallic nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Czeschka, Franz Dominik

    2011-09-05

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

  7. Cerebral hemodynamic changes measured by gradient-echo or spin-echo bolus tracking and its correlation to changes in ICA blood flow measured by phase-mapping MRI

    DEFF Research Database (Denmark)

    Marstrand, J.R.; Rostrup, Egill; Garde, Ellen

    2001-01-01

    Changes in cerebral blood flow (CBF) induced by Acetazolamide (ACZ) were measured using dynamic susceptibility contrast MRI (DSC-MRI) with both spin echo (SE) EPI and gradient echo (GE) EPI, and related to changes in internal carotid artery (ICA) flow measured by phase-mapping. Also examined...... increase in CBF and CBV in response to ACZ, while SE-EPI measured a significant increase in CBV and MTT. CBV and MTT change measured by SE-EPI was sensitive to previous bolus injections. There was a significant linear relation between change in CBF measured by GE-EPI and change in ICA flow. In conclusion...

  8. [Impacts of rail transit in Shanghai on its urban land use change].

    Science.gov (United States)

    Li, Cheng; Li, Jun-Xiang; Li, Rong; Xu, Ming-Ce; Qin, Hai

    2008-07-01

    By using the land use data interpreted with 1:50,000 color-infrared aerial photos of Shanghai collected in 1989 and 2005, and based on Geographic Information System (GIS) techniques, the impacts of urban rail transit (URT) development in Shanghai on its urban land use change was quantitatively analyzed, and a preliminary prediction of the land use change from 2010 to 2025 was made with Markov probability models. The results showed that the URT accelerated the land use change, particularly from an agricultural dominated natural landscape in 1989 to a high-value man-made urban landscape primarily composed of residence and public facilities. URT increased the land use rate in the study area. From 1989 to 2005, public facility land, green space, agriculture land, land for other uses (primarily used for construction), and water area changed greatly, with the greatest change rate of the land for other uses and the lowest one of water area. From 2010 to 2025, the areas and proportions of agriculture land and water area would keep on decreasing, while those of man-made landscapes including residence and public facilities would increase continuously. From the viewpoints of increasing land use rate and its gain, the present land use structure along Shanghai URT should be further regulated to improve the intensive and sustainable use of land resources.

  9. Multiferroics with spiral spin orders.

    Science.gov (United States)

    Tokura, Yoshinori; Seki, Shinichiro

    2010-04-12

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

  10. Land cover change using an energy transition paradigm in a statistical mechanics approach

    Science.gov (United States)

    Zachary, Daniel S.

    2013-10-01

    This paper explores a statistical mechanics approach as a means to better understand specific land cover changes on a continental scale. Integrated assessment models are used to calculate the impact of anthropogenic emissions via the coupling of technoeconomic and earth/atmospheric system models and they have often overlooked or oversimplified the evolution of land cover change. Different time scales and the uncertainties inherent in long term projections of land cover make their coupling to integrated assessment models difficult. The mainstream approach to land cover modelling is rule-based methodology and this necessarily implies that decision mechanisms are often removed from the physical geospatial realities, therefore a number of questions remain: How much of the predictive power of land cover change can be linked to the physical situation as opposed to social and policy realities? Can land cover change be understood using a statistical approach that includes only economic drivers and the availability of resources? In this paper, we use an energy transition paradigm as a means to predict this change. A cost function is applied to developed land covers for urban and agricultural areas. The counting of area is addressed using specific examples of a Pólya process involving Maxwell-Boltzmann and Bose-Einstein statistics. We apply an iterative counting method and compare the simulated statistics with fractional land cover data with a multi-national database. An energy level paradigm is used as a basis in a flow model for land cover change. The model is compared with tabulated land cover change in Europe for the period 1990-2000. The model post-predicts changes for each nation. When strong extraneous factors are absent, the model shows promise in reproducing data and can provide a means to test hypothesis for the standard rules-based algorithms.

  11. A typical example of a photomagnetic study carried out on a spin ...

    Indian Academy of Sciences (India)

    Keywords. Spin crossover; coordination chemistry; magnetism; photomagnetism. 1. Introduction. In the domain of transition metal complexes, there are several possibilities to induce light sensitive electronic changes accompanied by a drastic modification of magne- tic and/or optical properties, like metal-centred thermal.

  12. Cooperativity of Spin Crossover Complexes: Combining Periodic Density Functional Calculations and Monte Carlo Simulation

    Directory of Open Access Journals (Sweden)

    Lars Kreutzburg

    2017-02-01

    Full Text Available The total enthalpies of the 16 different spin configurations that can be realized in the unit cell of the archetype spin crossover complex [Fe(phen2(NCS2] (phen = 1,2-phenanthroline were calculated, applying periodic density functional theory combined with the Hubbard model and the Grimme-D2 dispersion correction (DFT+U+D2. The obtained enthalpy differences between the individual spin configurations were used to determine spin couplings of an Ising-like model, and subsequent Monte Carlo simulations for this model allowed the estimation of the phenomenological interaction parameter Γ of the Slichter–Drickamer model, which is commonly used to describe the cooperativity of the spin transition. The calculation procedure described here-which led to an estimate of about 3 kJ·mol-1 for Γ, in good agreement with experiment—may be used to predict from first principles how modifications of spin crossover complexes can change the character of the spin transition from gradual to abrupt and vice versa.

  13. High temperature spin state transitions in misfit-layered Ca{sub 3}Co{sub 4}O{sub 9}

    Energy Technology Data Exchange (ETDEWEB)

    Altin, S.; Aksan, M.A., E-mail: mehmet.aksan@inonu.edu.tr; Bayri, A.

    2014-02-25

    Highlights: • Ca{sub 3}Co{sub 4}O{sub 9} system has been fabricated using the solid-state technique. • There is an anomaly in magnetic the susceptibility χ between 680 and 920 K. • The anomaly is related to a critical threshold number of the high spin Co-ions. • The anomaly was also observed in the B and Sb-substituted Ca{sub 3}Co{sub 4}O{sub 9}. -- Abstract: This study reports high temperature magnetic properties of the unsubstituted one together with B and Sb-substituted Ca{sub 3}Co{sub 4}O{sub 9} system. The measured data indicated that there is an anomaly in the magnetic susceptibility, χ, between 680 and 920 K. It is believed that this anomaly is related to a critical threshold number of the high spin Co-ions such that when this threshold number is achieved, some exchange interactions between Co{sup 3+} and Co{sup 4+} take place which causes an abrupt increase in the χ–T curve. The anomaly was further investigated with B and Sb-substitutions. It is realized that both dopants promote more Co-ions in the rock salt unit cell to high spin state.

  14. Transitions in care during the end of life: changes experienced following enrolment in a comprehensive palliative care program

    Directory of Open Access Journals (Sweden)

    Critchley Patrick

    2005-02-01

    Full Text Available Abstract Background Transitions in the location of care and in who provides such care can be extremely stressful for individuals facing death and for those close to them. The objective of this study was to describe the distribution of transitions in care experienced by palliative care patients following admission to a comprehensive palliative care program (PCP. A better understanding of these transitions may aid in reducing unnecessary change, help predict care needs, enhance transitions that improve quality of life, guide health care system communication links and maximize the cost-effective utilization of different care settings and providers. Methods Transition and demographic information pertaining to all patients registered in the PCP at the Queen Elizabeth II Health Sciences Centre (QEII, Halifax, Nova Scotia, Canada between January 1, 1998 and December 31, 2002 and who died on or prior to December 31, 2002 was extracted from the PCP database and examined. A transition was defined as either: (1 a change in location of where the patient was cared for by the PCP or, (2 a change in which clinical service provided care. Descriptive analysis provided frequencies and locations of transitions experienced from time of PCP admission to death and during the final two and four weeks of life, an examination of patient movement and a summary of the length of stay spent by patients at each care location. Results Over the five year period, 3974 adults admitted to the QEII PCP experienced a total of 5903 transitions (Mean 1.5; standard deviation 1.8; median 1. Patients with no transitions (28% differed significantly from those who had experienced at least one transition with respect to survival time, age, location of death and diagnosis (p Conclusion A relatively small number of patients under the care of the PCP at the end of life, made several transitions in care setting or service provider. These particular patients need closer scrutiny to understand

  15. Urbanization and environmental change during the economic transition on the Mongolian Plateau: Hohhot and Ulaanbaatar.

    Science.gov (United States)

    Fan, Peilei; Chen, Jiquan; John, Ranjeet

    2016-01-01

    Driven by drastic socioeconomic changes in China and Mongolia, urbanization has become one of the most significant driving forces in the transformation of the Mongolian Plateau in the past 30 years. Using Hohhot and Ulaanbaatar as case studies, we developed a holistic approach to examine the socioeconomic and natural driving forces for urbanization and to investigate the impact on the urban environment. We used a multidisciplinary approach and relied on a variety of data sources to assess the changes of the landscape and environment of the two cities. We detected a rapid urbanization in Hohhot and Ulaanbaatar, both in terms of urban population growth and urban land expansion, from 1990 to 2010, with a much faster speed in 2000-2010. The local geo-physical conditions have constrained the spatial direction of expansion. Ulaanbaatar lagged behind Hohhot for about a decade when measured by indicators of urban population and urban land. Both cities have a degraded urban environment and a growing air pollution epidemic. While Hohhot had worse air pollution than Ulaanbaatar in the early 2000s, the gap between the two cities became smaller after 2010. The research presented here highlights the following as key determinants for urbanization and environmental change: (1) the co-evolution of urbanization, economic development, and environmental change; (2) the urbanization of transitional economies driven by the change of the economic structure, i.e., the development by both manufacturing and tertiary sectors and the change in the primary sector; and (3) the recent institutional changes and increased integration with the global economy. Copyright © 2015 Elsevier Inc. All rights reserved.

  16. Signs of critical transition in the Everglades wetlands in response to climate and anthropogenic changes.

    Science.gov (United States)

    Foti, Romano; del Jesus, Manuel; Rinaldo, Andrea; Rodriguez-Iturbe, Ignacio

    2013-04-16

    The increasing pressure of climatic change and anthropogenic activities is predicted to have major effects on ecosystems around the world. With their fragility and sensitivity to hydrologic shifts and land-use changes, wetlands are among the most vulnerable of such ecosystems. Focusing on the Everglades National Park, we here assess the impact of changes in the hydrologic regime, as well as habitat loss, on the spatial configuration of vegetation species. Because the current structuring of vegetation clusters in the Everglades exhibits power-law behavior and such behavior is often associated with self-organization and dynamics occurring near critical transition points, the quantification and prediction of the impact of those changes on the ecosystem is deemed of paramount importance. We implement a robust model able to identify the main hydrologic and local drivers of the vegetation species spatial structuring and apply it for quantitative assessment. We find that shifts in the hydropatterns will mostly affect the relative abundance of species that currently colonize specific hydroperiod niches. Habitat loss or disruption, however, would have a massive impact on all plant communities, which are found to exhibit clear threshold behaviors when a given percentage of habitable habitat is lost.

  17. Understanding Personal Change in a Women’s Faith-Based Transitional Center

    Directory of Open Access Journals (Sweden)

    Ariana Mishay Stone

    2011-06-01

    Full Text Available An impressive research literature has emerged that identifies linkages between religion and a wide range of attitudes, behaviors, and life events. We contribute to this literature by exploring how women undergoing difficult life circumstances—such as incarceration, drug and alcohol addiction, domestic violence, unemployment, and homelessness—use faith to cope with and change these circumstances. To address this issue we analyze semi-structured interviews with 40 residents of a faith-based transitional center for women in the Southern United States. The residents outline a narrative of change in which they distinguish between the “old self” and “new self.” The narratives also specify the role of religiosity in facilitating change, the creation of a faith-based identity, and the strategies used for maintaining change. We conclude with implications for faith-based treatment programs, local pastors and religious congregants involved in social outreach ministry, sociology of religion scholars, and policy makers.

  18. Navigations and governance in the Danish energy transition reflecting changing Arenas of Development, controversies and policy mixes

    DEFF Research Database (Denmark)

    Jørgensen, Michael Søgaard; Jørgensen, Ulrik; Jensen, Jens Stissing

    2017-01-01

    -organising actor-constellations are constitutional for arenas and define their boundaries and the policies employed. We discuss the historic transitions in relation to four focal areas of Danish attempts to become independent of fossil energy: wind-power integration in the energy system, energy savings, biomass...... and sustainable mobility. The analysis demonstrates the conflicts and mixes of policy measures that have moved transition processes forward, but sometimes also stalling them. The analysis shows how changing controversies, arena configurations and policy mixes move forward the energy transition process.......The article discusses transition dynamics towards a Danish low-carbon society based on studies of energy production and consumption. This article shows how the Arena of Development and policy mix approaches may inform the analysis of system transition to a low carbon society. The Arena...

  19. Nanomechanical morphology of amorphous, transition, and crystalline domains in phase change memory thin films

    Science.gov (United States)

    Bosse, J. L.; Grishin, I.; Huey, B. D.; Kolosov, O. V.

    2014-09-01

    In the search for phase change materials (PCM) that may rival traditional random access memory, a complete understanding of the amorphous to crystalline phase transition is required. For the well-known Ge2Sb2Te5 (GST) and GeTe (GT) chalcogenides, which display nucleation and growth dominated crystallization kinetics, respectively, this work explores the nanomechanical morphology of amorphous and crystalline phases in 50 nm thin films. Subjecting these PCM specimens to a lateral thermal gradient spanning the crystallization temperature allows for a detailed morphological investigation. Surface and depth-dependent analyses of the resulting amorphous, transition and crystalline regions are achieved with shallow angle cross-sections, uniquely implemented with beam exit Ar ion polishing. To resolve the distinct phases, ultrasonic force microscopy (UFM) with simultaneous topography is implemented revealing a relative stiffness contrast between the amorphous and crystalline phases of 14% for the free film surface and 20% for the cross-sectioned surface. Nucleation is observed to occur preferentially at the PCM-substrate and free film interface for both GST and GT, while fine subsurface structures are found to be sputtering direction dependent. Combining surface and cross-section nanomechanical mapping in this manner allows 3D analysis of microstructure and defects with nanoscale lateral and depth resolution, applicable to a wide range of materials characterization studies where the detection of subtle variations in elastic modulus or stiffness are required.

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

    Directory of Open Access Journals (Sweden)

    Saburo Takahashi and Sadamichi Maekawa

    2008-01-01

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