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Transitions De Phases Quantiques Dans Le Compose Quasi 1d Antiferromagnetique De Type Ising Baco2v2o8
Download Transitions De Phases Quantiques Dans Le Compose Quasi 1d Antiferromagnetique De Type Ising Baco2v2o8 full books in PDF, epub, and Kindle. Read online Transitions De Phases Quantiques Dans Le Compose Quasi 1d Antiferromagnetique De Type Ising Baco2v2o8 ebook anywhere anytime directly on your device. Fast Download speed and no annoying ads. We cannot guarantee that every ebooks is available!
Book Synopsis Transitions de Phases Quantiques Dans Le Composé Quasi-1D Antiferromagnétique de Type Ising BaCo2V2O8 by : Quentin Faure
Download or read book Transitions de Phases Quantiques Dans Le Composé Quasi-1D Antiferromagnétique de Type Ising BaCo2V2O8 written by Quentin Faure and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This manuscript is devoted to the study of quantum phase transitions in the BaCo2V2O8 oxide, a quasi-one dimensional antiferromagnet consisting of spin chains of cobalt magnetic ions carrying an effective spin S = 1/2 showing a strong Ising-like anisotropy. To achieve this, we have studied BaCo2V2O8 under the effect of different physical parameters.Our first study concerned the effect of a transverse magnetic field, i.e. applied perpendicularly to the Ising axis. It has been shown that when BaCo2V2O8 is subjected to such a field, an effective staggered magnetic field is induced perpendicularly to both the Ising-axis and the uniform applied field. Using neutron scattering experiments (both elastic and inelastic) compared to numerical calculations, we have proved that this staggered field competes with the Ising-like anisotropy. This leads to a very original quantum phase transition. Our system can actually be mapped onto a quantum field theory called “double sine-Gordon model”, describing the competition between two dual topological excitations. We have thus shown that BaCo2V2O8 under a transverse magnetic field is the first experimental realization of such a theory.The second study was devoted to the effect of a longitudinal magnetic field, i.e. a field applied parallel to the Ising-axis. The spin-dynamics have been investigated by means of inelastic neutron scattering experiments and it has been shown that above a critical field of 4 T, it corresponds to the one expected for a Tomonaga Luttinger liquid phase (TLL). Moreover, numerical calculations have shown that, because of the Ising-like anisotropy in this system, the majority of the spectral weight in the energy spectrum is carried by longitudinal spin fluctuations. This result is the signature of a quantum behavior without classical analogous with low energy longitudinal fluctuations driving the physics of the system. Finally, this is the first time that the dispersion spectrum for an Ising-like spin 1/2 chain could be probed in this TLL phase.The last two studies are preliminary work. The phase diagram of BaCo2V2O8 has been probed by calorimetric measurements under pressure and under a longitudinal magnetic field. Pressures up to 10 GPa have been obtained using a diamond anvil cell. We have then performed specific heat measurements allowing us to investigate the effect of pressure on the Hamiltonian of BaCo2V2O8 through its (H, P, T) phase diagram. Finally, we have also started to study the effect of the substitution of magnetic ions Co2+ by non-magnetic impurities Mg2+. The neutron diffraction experiments under a longitudinal magnetic field have shown that the critical temperature and critical field decrease proportionally to the concentration of impurities. The spin-dynamics at zero-field has also been investigated and reveals the appearance of non-dispersive magnetic modes, which possibly comes from the finite size effect of the spin chains segmented by the non-magnetic impurities.In conclusion, our experimental studies associated to numerical calculations allowed us to unveil a very rich physics in this model compound for the study of quantum magnetism and quantum phase transitions.
Book Synopsis Transitions de phases magnétiques dans des systèmes de spins quantiques à basse dimension by : Emmanuel Canévet
Download or read book Transitions de phases magnétiques dans des systèmes de spins quantiques à basse dimension written by Emmanuel Canévet and published by . This book was released on 2010 with total page 129 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cette thèse porte sur l'étude de trois systèmes de spins basse dimension par diffraction et diffusion inélastique de neutrons. Dans le composé DMACuCl3, les mesures macroscopiques semblent indiquer la coexistence de deux types de dimères : antiferromagnétique et ferromagnétique. Une étude par diffraction nous a permis de déterminer sa structure magnétique en champ nul qui prouve l'existence des deux dimères de manière irrévocable. Il a été montré que le composé de type Ising BaCo2V2O8 serait le premier système présentant un ordre magnétique incommensurable longitudinal (ICL) sous champ. Tout d'abord, nous avons déterminé la structure magnétique en champ nul. Ensuite, nous avons suivi l'évolution du vecteur de propagation en fonction du champ magnétique caractérisant ainsi l'entrée dans la phase ICL à Hc = 3.9 T. La détermination de l'ordre magnétique de la phase ICL confirme que BaCo2V2O8 est le premier composé présentant un ordre magnétique colinéaire à la direction du champ. Il a été montré que le composé organique DF5PNN est bien décrit à basse température par des chaînes de spins à couplages alternés. Or la structure cristallographique connue à température ambiante implique des couplages uniformes. Notre étude par diffraction montre l'existence d'une transition structurale à basse température (Tc = 450 mK) faisant passer du groupe d'espace C2/c à Pc, et expliquant la nature alternée des interactions. Nous avons également caractérisé une transition structurale induite sous champ (Hc = 1.1 T) faisant revenir le groupe d'espace à C2/c. Cette transition implique un retour à l'uniformité des échanges, ce que nous avons confirmé en étudiant les excitations magnétiques.
Book Synopsis High Performance Soft Magnetic Materials by : Arcady Zhukov
Download or read book High Performance Soft Magnetic Materials written by Arcady Zhukov and published by Springer. This book was released on 2017-01-24 with total page 223 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides comprehensive coverage of the current state-of-the-art in soft magnetic materials and related applications, with particular focus on amorphous and nanocrystalline magnetic wires and ribbons and sensor applications. Expert chapters cover preparation, processing, tuning of magnetic properties, modeling, and applications. Cost-effective soft magnetic materials are required in a range of industrial sectors, such as magnetic sensors and actuators, microelectronics, cell phones, security, automobiles, medicine, health monitoring, aerospace, informatics, and electrical engineering. This book presents both fundamentals and applications to enable academic and industry researchers to pursue further developments of these key materials. This highly interdisciplinary volume represents essential reading for researchers in materials science, magnetism, electrodynamics, and modeling who are interested in working with soft magnets.
Book Synopsis Physical Properties of Amorphous Materials by : David Adler
Download or read book Physical Properties of Amorphous Materials written by David Adler and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Institute for Amorphous Studies was founded in 1982 as the international center for the investigation of amorphous mate rials. It has since played an important role in promoting the und er standing of disordered matter in general. An Institute lecture series on "Fundamentals of Amorphous Materials and Devices" was held during 1982-83 with distinguished speakers from universities and industry. These events were free and open to the public ,and were attended by many representatives of the scientific community. The lectures themselves were highly successful inasmuch as they provided not only formal instruction but also an opportunity for vigorous and stimulating debate. That last element could not be captured within the pages of a book I but the lectures concentrated on the latest advances in the field I which is why their essential contents are he re reproduced in collective form. Together they constitute an interdisciplinary status report of the field. The speakers brought many different viewpoints and a variety of back ground experiences io bear on the problems involved I but though language and conventions vary I the essential unity of the concerns is very clear I as indeed are the ultimate benefits of the many-sided approach.
Book Synopsis Graphite Intercalation Compounds II by : Hartmut Zabel
Download or read book Graphite Intercalation Compounds II written by Hartmut Zabel and published by Springer Science & Business Media. This book was released on 2013-03-07 with total page 442 pages. Available in PDF, EPUB and Kindle. Book excerpt: The research on graphite intercalation compounds often acts as a forerunner for research in other sciences. For instance, the concept of staging, which is fundamental to graphite intercalation compounds, is also relevant to surface science in connection with adsorbates on metal surfaces and to high-temperature superconducting oxide layer materials. Phonon-folding and mode-splitting effects are not only basic to graphite intercalation compounds but also to polytypical systems such as supercon ductors, superlattices, and metal and semiconductor superlattices. Charge transfer effects playa tremendously important role in many areas, and they can be most easily and fundamentally studied with intercalated graphite. This list could be augmented with many more examples. The important message, however, is that graphite inter calation compounds represent a class of materials that not only can be used for testing a variety of condensed-matter concepts, but also stimulates new ideas and approaches. This volume is the second of a two-volume set. The first volume addressed the structural and dynamical aspects of graphite intercalation compounds, together with the chemistry and intercalation of new compounds. This second volume provides an up-to-date status report from expert researchers on the transport, magnetic, elec tronic and optical properties ofthis unique class of materials. The band-structure cal culations of the various donor and acceptor compounds are discussed in depth, and detailed reviews are provided ofthe experimental verification ofthe electronic struc ture in terms of their photoemission spectra and optical properties.
Book Synopsis Mechanical Engineering and Materials by : Wen Jin
Download or read book Mechanical Engineering and Materials written by Wen Jin and published by Trans Tech Publications Ltd. This book was released on 2012-01-24 with total page 2080 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volume is indexed by Thomson Reuters CPCI-S (WoS). The present papers, drawn from both academia and industry, reflect the international flavour of this event; devoted to the topics of: Materials Science and Engineering, Materials Properties, Measuring Methods and Applications, Methodology of Research and Analysis and Modelling, Materials Manufacturing and Processing, Nanoscience and Nanotechnology, Mechanical Engineering, Design and Manufacturing, etc.
Book Synopsis Frustrated Spin Systems (Third Edition) by : Hung-The Diep
Download or read book Frustrated Spin Systems (Third Edition) written by Hung-The Diep and published by World Scientific Publishing Company. This book was released on 2020-06-09 with total page 750 pages. Available in PDF, EPUB and Kindle. Book excerpt: Frustrated spin systems have been first investigated five decades ago. Well-known examples include the Ising model on the antiferromagnetic triangular lattice studied by G H Wannier in 1950 and the Heisenberg helical structure discovered independently by A Yoshimori, J Villainn and T A Kaplan in 1959. However, extensive investigations on frustrated spin systems have really started with the concept of frustration introduced at the same time by G Toulouse and by J Villain in 1977 in the context of spin glasses. The frustration is generated by the competition of different kinds of interaction and/or by the lattice geometry. As a result, in the ground state all bonds are not fully satisfied. In frustrated Ising spin systems, a number of spins behave as free spins. In frustrated vector spin systems, the ground-state configuration is usually non-collinear. The ground state of frustrated spin systems is therefore highly degenerate and new induced symmetries give rise to unexpected behaviors at finite temperatures. Many properties of frustrated systems are still not well understood at present. Theoretically, recent studies shown in this book reveal that established theories, numerical simulations as well as experimental techniques have encountered many difficulties in dealing with frustrated systems. In some sense, frustrated systems provide an excellent testing ground for approximations and theories. Experimentally, more and more frustrated materials are discovered with interesting properties for applications.
