Neutron Scattering Studies of Pyrochlore Quantum Magnets PDF Download

Author: Viviane Peçanha Antonio
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Author:
Publisher: Elsevier
ISBN: 0128020938
Category : Science
Languages : en
Pages : 534

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Book Description
Neutron Scattering - Magnetic and Quantum Phenomena provides detailed coverage of the application of neutron scattering in condensed matter research. The book's primary aim is to enable researchers in a particular area to identify the aspects of their work where neutron scattering techniques might contribute, conceive the important experiments to be done, assess what is required to carry them out, write a successful proposal for one of the major user facilities, and perform the experiments under the guidance of the appropriate instrument scientist. An earlier series edited by Kurt Sköld and David L. Price, and published in the 1980s by Academic Press as three volumes in the series Methods of Experimental Physics, was very successful and remained the standard reference in the field for several years. This present work has similar goals, taking into account the advances in experimental techniques over the past quarter-century, for example, neutron reflectivity and spin-echo spectroscopy, and techniques for probing the dynamics of complex materials of technological relevance. This volume complements Price and Fernandez-Alonso (Eds.), Neutron Scattering - Fundamentals published in November 2013. Covers the application of neutron scattering techniques in the study of quantum and magnetic phenomena, including superconductivity, multiferroics, and nanomagnetism Presents up-to-date reviews of recent results, aimed at enabling the reader to identify new opportunities and plan neutron scattering experiments in their own field Provides a good balance between theory and experimental techniques Provides a complement to Price and Fernandez-Alonso (Eds.), Neutron Scattering - Fundamentals published in November 2013

Author: Chiron Jeeb Mukherjee
Publisher:
ISBN:
Category : Antiferromagnetism
Languages : en
Pages : 418

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Author: David Macdougal
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Andreas Michels
Publisher: Oxford University Press
ISBN: 0198855176
Category : Science
Languages : en
Pages : 374

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Magnetic Small-Angle Neutron Scattering provides the first extensive treatment of magnetic small-angle neutron scattering (SANS). The theoretical background required to compute magnetic SANS cross sections and correlation functions related to long-wavelength magnetization structures is laidout. The concepts are scrutinized based on the discussion of experimental neutron data. Regarding prior background knowledge, some familiarity with the basic magnetic interactions and phenomena as well as scattering theory is desired.Besides exposing the different origins of magnetic SANS, and furnishing the basics of the magnetic SANS technique in early chapters, a large part of the book is devoted to a comprehensive treatment of the continuum theory of micromagnetics, as it is relevant for the study of the elastic magneticSANS cross section. Analytical expressions for the magnetization Fourier components allow to highlight the essential features of magnetic SANS and to analyze experimental data both in reciprocal, as well as in real space. Later chapters provide an overview on the magnetic SANS of nanoparticles andso-called complex systems (e.g., ferrofluids, magnetic steels, spin glasses and amorphous magnets). It is this subfield where major progress is expected to be made in the coming years, mainly via the increased usage of numerical micromagnetic simulations (Chapter 7), which is a very promisingapproach for the understanding of the magnetic SANS from systems exhibiting nanoscale spin inhomogeneity.

Author: Ewald Balcar
Publisher: Clarendon Press
ISBN: 019158911X
Category : Science
Languages : en
Pages : 241

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The techniques of magnetic neutron and photon scattering provide information on the electronic properties of materials that is obtainable in no other way. With both techniques information on an atomic scale is obtained on the spatial and temporal developments of the spin and current densities which are fundamental quantities in a basic understanding of magnetic phenomena. To date most magnetic scattering studies have used neutron beams, and the use of photon beams is, relatively speaking, in its infancy. This book is the first monograph devoted to the theory required for a full interpretation of magnetic scattering experiments. It is designed to meet the needs of postgraduates and researchers new to the techniques. At the same time, the requirements of theoretical chemists and physicists are catered for through chapters that present the basic formalism in detail. Special features of the book include extensive tables of quantities that occur frequently in applications of theory, and a number of worked examples.

Author: Oliver Pieper
Publisher:
ISBN: 9783832527303
Category :
Languages : en
Pages : 270

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This thesis deals with the investigation of two different types of low-dimensional quantum magnets using the technique of neutron scattering.In the first part, the magnetic properties of three Mn_6-based single molecule magnets are explored by means of inelastic neutron scattering. The experimental data reveal that small structural distortions of the molecular geometry produce a significant effect on the energy level diagram and therefore on the magnetic properties of the molecules. It will be shown that the giant spin model completely fails to describe the spin level structure of the ground spin multiplets and that the excited S-multiplets play a key role in determining the effective energy barrier for the magnetization reversal.The second part of this thesis presents an in-depth study of the nuclear and magnetic properties of the quasi-one-dimensional Heisenberg antiferromagnet CaV_2O_4. The magnetism in this system arises from the partially filled t_{2g-levels of the V^{3+-ions, which in addition give an orbital degree of freedom to the system.Single crystal and powder neutron diffraction as well as neutron spectroscopy are used to determine the nuclear and magnetic structure as well as the complex excitation spectrum of CaV_2O_4. The results are analysed theoretically and from this the leading exchange paths are deduced and discussed in terms of orbital ordering.

Author: Albert Furrer
Publisher: World Scientific
ISBN: 9814548901
Category : Science
Languages : en
Pages : 284

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The proceedings provide a topical survey of the static and dynamical magnetic properties of condensed matter studied by neutron scattering which has been the key technique in this field for a long time. The static aspects deal with the determination of long-range ordered spin structures and magnetization densities. The dynamic aspects concentrate on the determination of magnetic excitations such as spin waves and crystal-field transitions. The use of polarized-neutron techniques is particularly emphasized. All these topics are thoroughly introduced, methodically discussed, and highlighted with recent experimental results obtained for a vast variety of magnetic materials (e.g., strongly correlated electron systems, multilayers, nanocrystals, molecular complexes, etc.) by acknowledged experts. Other experimental methods (x-ray scattering, muon spin rotation) in the study of magnetism are compared to neutron scattering.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 9

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In this paper, I shall attempt to review what has been learned about magnetism in the high-{Tc} family of compounds using neutron scattering techniques. Whether or not it is true that magnetic effects are involved in an essential way in the mechanism for superconductivity in these materials (a point which has not yet been firmly established), they offer fascinating examples for the study of magnetism for its own sake, being realizations of spin 1/2 2D quantum antiferromagnets. Further, the rare earth spins in these materials also order at low temperatures reminiscent of the coexistence of antiferromagnetism and superconductivity in the earlier well-studied families of magnetic superconductors such as ErRh4B4 and the Chevrel-phase compounds, with the difference that the ordering here is primarily 2D in character.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 203

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The behavior of magnetic systems in the extreme quantum limit is one of the most interesting forefront areas in condensed matter physics. This dissertation investigates two particularly interesting quantum magnets: LiVO2 and DMACuCl3. Systematic studies were performed on single crystal samples using different experimental techniques, especially inelastic neutron scattering. Detailed experimental results and corresponding model calculations are presented and discussed in this dissertation. LiVO2 is a good candidate to study the interplay between ʺmagnetic frustrationʺ and orbital ordering. V3+ ions in LiVO2 form a triangular lattice involving threefold degenerate t2g orbitals. LiVO2 undergoes a first order phase transition at Tt = 500 K accompanied by a large reduction of the magnetic susceptibility in the low temperature phase. The origin of this phase transition has been associated with a peculiar type of t2g orbital ordering resulting in the formation of vanadium trimer clusters with a spin-singlet ground state. Our inelastic neutron scattering experiments reveal multiple magnetic excitations with energy transfer as large as several hundreds of meV associated with the low temperature orbitally ordered phase. This can not be explained by a simple ʺspin-onlyʺ isolated trimer model. Model calculations including a Kugel-Khomskii orbital-ordering term yield qualitatively similar spectra suggesting that a new type of excitation, which we refer to as ʺcluster orbitonʺ, has been observed in LiVO2. DMACuCl3 was proposed as a S = 1/2 FM-AFM alternating-sign chain along the a-axis. However, our inelastic neutron scattering experiments indicate that the strong magnetic coupling in DMACuCl3 is along the b-axis, and the magnetic excitation spectrum is dominated by the FM-AFM alternating chain with J (subscript FM) = -1.2(1) meV and J(subscript AFM) = 1.3(2) meV. Furthermore, recent studies show that DMACuCl3 undergoes a structural phase transition at Tt = 285 K. Below T(subscript t), the low temperature crystal structure suggests that DMACuCl3 contains two types of dimers: FM and AFM dimers. Inelastic neutron scattering results suggest a two chain model along the b-axis for DMACuCl3. This research is conducted under the supervision of the authorʹs advisors: Dr. David G. Mandrus at material science and technology division and Dr. Stephen E. Nagler at center for neutron scattering, Oak Ridge National Laboratory.