Ab Initio Theory Of Magnetic Ordering
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Ab Initio Theory Of Magnetic Ordering
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Author : Eduardo Mendive Tapia
language : en
Publisher: Springer Nature
Release Date : 2020-01-03
Ab Initio Theory Of Magnetic Ordering written by Eduardo Mendive Tapia and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020-01-03 with Science categories.
Many technological applications exploit a variety of magnetic structures, or magnetic phases, to produce and optimise solid-state functionality. However, most research advances are restricted to a reduced number of phases owing to computational and resource constraints. This thesis presents an ab-initio theory to efficiently describe complex magnetic phases and their temperature-dependent properties. The central assumption is that magnetic phases evolve slowly compared with the underlying electronic structure from which they emerge. By describing how the electronic structure adapts to the type and extent of magnetic order, a theory able to describe multi-spin correlations and their effect on the magnetism at finite temperature is obtained. It is shown that multi-spin correlations are behind the temperature and magnetic field dependence of the diverse magnetism in the heavy rare earth elements. Magnetically frustrated Mn-based materials and the effect of strain are also investigated. These studies demonstrate that the performance of solid-state refrigeration can be enhanced by multi-spin effects.
Ab Initio Investigations Of Magnetic Properties Of Ultrathin Transition Metal Films On 4d Substrates
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Author : Ali Al-Zubi
language : en
Publisher: Forschungszentrum Jülich
Release Date : 2010
Ab Initio Investigations Of Magnetic Properties Of Ultrathin Transition Metal Films On 4d Substrates written by Ali Al-Zubi and has been published by Forschungszentrum Jülich this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
Ab Initio Theory Of The Magnetic Properties Of Heterogeneous Nanostructures
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Author : Manuel dos Santos Dias
language : en
Publisher:
Release Date : 2011
Ab Initio Theory Of The Magnetic Properties Of Heterogeneous Nanostructures written by Manuel dos Santos Dias and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
This thesis presents a general formalism for a Density Functional Theory description of the magnetic state of a heterogeneous system, from its paramagnetic high-temperature state to the magnetically ordered ground state. The key ingredient is the identification of localised magnetic moments as emergent electronic degrees of freedom, and the evolution of their orientations under a classical spin Hamiltonian dictated by the underlying electronic structure, computed using Multiple Scattering Theory. The magnetic interactions are contained in the spin-spin correlation function, derived in a linear response approach, and are fully anisotropic, as relativistic effects are accounted for. A range of applications is given. A Mn monolayer on the W(001) is shown to favour a cycloidal spin spiral as ground state, with a well-defined rotational sense due to unidirectional anisotropic interactions. The antiferromagnetism of Mn monolayers on X(111), with X = Pd, Pt, Ag and Au, is analysed, and the triangular Néel state is shown to possess a well-defined chirality pattern. Calculations for bulk zinc{blende MnSb characterise the half-metallic state as being robust against magnetic disorder; this particular polymorph was discovered in epitaxial form by experimentalists at the University of Warwick, and shows promise for spintronics applications. Bulk Co in the hcp and fcc structure reveals the strong feedback between the magnitude of the spin moment and the degree of magnetic order, through the corresponding electronic structure. To conclude, an FeRh film embedded in V is considered. The magnetisation profile corresponding to the imposed antiferromagnetic order is computed self-consistently, and shows the stabilisation of the Fe layers close to the interface with V by those in the interior of the film.
Controlling Magnetic And Ferroelectric Order Through Geometry
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Author :
language : en
Publisher:
Release Date : 2016
Controlling Magnetic And Ferroelectric Order Through Geometry written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
We have focused on the synthesis, characterization, and ab initio theory on multi-functional mixed-metal fluorides. With funding from the DOE, we have successfully synthesized and characterized a variety of mixed metal fluoride materials.
Theory Of Itinerant Electron Magnetism
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Author : Jürgen Kübler
language : en
Publisher: Oxford University Press
Release Date : 2017-03-23
Theory Of Itinerant Electron Magnetism written by Jürgen Kübler and has been published by Oxford University Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017-03-23 with Science categories.
This book, in the broadest sense, is an application of quantum mechanics and statistical mechanics to the field of magnetism. Under certain well described circumstances, an immensely large number of electrons moving in the solid state of matter will collectively produce permanent magnetism. Permanent magnets are of fundamental interest, and magnetic materials are also of great practical importance as they provide a large field of technological applications. The physical details describing the many electron problem of magnetism are presented in this book on the basis of the local density functional approximation. The emphasis is on realistic magnets, for which the equations describing the many electron problem can only be solved by using computers. The great, recent and continuing improvements of computers are, to a large extent, responsible for the progress in the field. Along with a detailed introduction to the density functional theory, this book presents representative computational methods and provides the reader with a complete computer programme for the determination of the electronic structure of a magnet on a PC. A large part of the book is devoted to a detailed treatment of the connections between electronic properties and magnetism, and how they differ in the various known magnetic systems. Current trends are exposed and explained for a large class of alloys and compounds. The modern field of artificially layered systems - known as multilayers - and their industrial applications are dealt with in detail. Finally, an attempt is made to relate the rich thermodynamic properties of magnets to the ab initio results originating from the electronic structure.
Modelling Atomic Arrangements In Multicomponent Alloys
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Author : Christopher D. Woodgate
language : en
Publisher: Springer Nature
Release Date :
Modelling Atomic Arrangements In Multicomponent Alloys written by Christopher D. Woodgate and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on with categories.
A First Principles Approach To Modelling Magnetism Instrongly Correlated Electron Systems
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Author : Ian Hughes
language : en
Publisher:
Release Date : 2007
A First Principles Approach To Modelling Magnetism Instrongly Correlated Electron Systems written by Ian Hughes and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with categories.
We present an ab initio theoretical formalism for investigating the onset of magnetic order in strongly-correlated electron systems. The formalism is based on spin density functional theory, with a self-interaction corrected local density approximation (SIC-LDA). The self-interaction correction is implemented locally, within the KKR multiple-scattering method. Thermally induced magnetic fluctuations are treated using a mean-field 'disordered local moment' (DLM) approach and we use a linear ·response technique to generate the paramagnetic spin susceptibility. We apply the formalism to the heavy rare earth metals, where the magnetic ordering tendencies are analysed in terms of the underlying electronic structure. The formation of incommensurate magnetic structures is shown to be promoted through a Fermi surface nesting mechanism. Our calculations yield an accurate, parameter free, estimate of the magnetic ordering temperature of gadolinium. Using this element as a magnetic prototype, we propose a 'unified phase diagram', from which the magnetic ordering tendencies of any heavy rare earth system can be found. This diagram is used to predict critical alloy concentrations, at which new magnetic phases appears. We also examine magnetic ordering in transition metal oxides and outline how our first principles linear response approach can be adapted to study compositional correlations, .which we illustrate by investigating the presence of atomic short range order in gadolinium-yttrium alloys.
Handbook Of Materials Modeling
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Author : Sidney Yip
language : en
Publisher: Springer Science & Business Media
Release Date : 2007-11-17
Handbook Of Materials Modeling written by Sidney Yip and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007-11-17 with Science categories.
The first reference of its kind in the rapidly emerging field of computational approachs to materials research, this is a compendium of perspective-providing and topical articles written to inform students and non-specialists of the current status and capabilities of modelling and simulation. From the standpoint of methodology, the development follows a multiscale approach with emphasis on electronic-structure, atomistic, and mesoscale methods, as well as mathematical analysis and rate processes. Basic models are treated across traditional disciplines, not only in the discussion of methods but also in chapters on crystal defects, microstructure, fluids, polymers and soft matter. Written by authors who are actively participating in the current development, this collection of 150 articles has the breadth and depth to be a major contributor toward defining the field of computational materials. In addition, there are 40 commentaries by highly respected researchers, presenting various views that should interest the future generations of the community. Subject Editors: Martin Bazant, MIT; Bruce Boghosian, Tufts University; Richard Catlow, Royal Institution; Long-Qing Chen, Pennsylvania State University; William Curtin, Brown University; Tomas Diaz de la Rubia, Lawrence Livermore National Laboratory; Nicolas Hadjiconstantinou, MIT; Mark F. Horstemeyer, Mississippi State University; Efthimios Kaxiras, Harvard University; L. Mahadevan, Harvard University; Dimitrios Maroudas, University of Massachusetts; Nicola Marzari, MIT; Horia Metiu, University of California Santa Barbara; Gregory C. Rutledge, MIT; David J. Srolovitz, Princeton University; Bernhardt L. Trout, MIT; Dieter Wolf, Argonne National Laboratory.
Handbook On The Physics And Chemistry Of Rare Earths
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Author :
language : en
Publisher: Elsevier
Release Date : 2011-09-22
Handbook On The Physics And Chemistry Of Rare Earths written by and has been published by Elsevier this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011-09-22 with Science categories.
This continuing authoritative series deals with the chemistry, materials science, physics and technology of the rare earth elements in an integrated manner. Each chapter is a comprehensive, up-to-date, critical review of a particular segment of the field. The work offers the researcher and graduate student a complete and thorough coverage of this fascinating field. REVIEW: "Highly experienced authors have written each review usually at a level suitable for advanced postgraduate students and research workers from a variety of fields. With the great richness of information involving references to other review articles written from different points of view, the books are an important reference source and should be on the shelves of most libraries." -- Journal of Applied Crystallography Authoritative Comprehensive Up-to-date Critical
Investigation Of Light Induced Ultrafast Magnetization Dynamics Using Ab Initio Methods
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Author : Philippe Scheid
language : en
Publisher:
Release Date : 2020
Investigation Of Light Induced Ultrafast Magnetization Dynamics Using Ab Initio Methods written by Philippe Scheid and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020 with categories.
This thesis begins with a review of the current experimental and theoretical state of the art related to the light-induced ultrafast demagnetization and the all-optical helicity-dependent switching. This is followed by an overview of density functional theory, upon which relies most of the work reported thereafter. The first set of results concerns the ab initio study of the effect of a rise in the electronic temperature on the magnetized matter properties, and more specifically Fe, Co, Ni and FePt. We show that the magnetic moment carried by each atom disappears at the so-called Stoner temperature, and that this phenomenon impacts the electronic energy and specific heat, even at low electronic temperature. Then, we show that upon an increase in the electronic temperature, the interatomic Heisenberg exchange, which is responsible for the magnetic ordering, decreases. Using the atomistic Langevin Landau-Lifshitz-Gilbert equation, we demonstrate that this decrease is enough to induce a large reduction of the average magnetization by creating transversal excitations. The second set of results regards the origin of the helicity-dependent light-induced dynamics. While the literature attributes it mainly to the inverse Faraday effect, we argue that another and novel phenomenon, which occurs during the absorption of the light, may be more suited to account for the experimental dynamics. Indeed, using the Fermi golden rule and ground state density functional theory calculations in Fe, Co, Ni and FePt, we show that, as the light is absorbed and electrons are excited, concurrently to the increase of the electronic energy, the spin-state is also changed in presence of spin-orbit coupling. This results in a difference in the value of the atomic magnetic moments, persisting even after the light is gone, as opposed to the inverse Faraday effect. Then, using real-time time-dependent density functional theory, we compute the magnetization dynamics induced by real optical and XUV femtosecond circularly polarized pulses. We show that, in both cases the dynamics is helicity-dependent and that this characteristic is largely amplified in the XUV regime involving the semi-core 3p states. Finally, we compare the relative role of the inverse Faraday effect and the magnetization induced during the absorption of the light and show that the latter plays a prominent role, especially after the light has gone, and in the XUV regime.