Nanoscale Phase Separation And Colossal Magnetoresistance

The study of the spontaneous formation of nanostructures in single crystals of several compounds is now a major area of research in strongly correlated electrons. These structures appear to originate in the competition of phases. The book addresses nanoscale phase separation, focusing on the manganese oxides known as manganites that have the colossal magnetoresistance (CMR) effect of potential relevance for device applications. It is argued that the nanostructures are at the heart of the CMR phenomenon. The book contains updated information on manganite research directed to experts, both theorists and experimentalists. However, graduate students or postdocs will find considerable introductory material, including elements of computational physics.

Colossal magnetoresistance materials, to which manganites and conventional ferromagnetic semiconductors belong, draw great attention because of their intriguing physical properties and the excellent prospects for their practical applications in electronic devices. In addition, magnetic semiconductors are basic materials for high-temperature conductors, and it is impossible to construct a theory of the latter without elucidating properties of the former. This book presents theoretical and experimental results on manganites and conventional magnetic semiconductors, with emphasis on the former. It is addressed mainly to researchers dealing with manganites or high-temperature superconductors, but is also useful for undergraduate and graduate students. Contents:Introduction and Necessary Information about Non-magnetic Semiconductors and Insulating Magnetic SystemsPrinciples of Theory of Conducting MagneticNon-degenerate Ferromagnetic SemiconductorsNon-degenerate Antiferromagnetic Semiconductors and Self-trapped StatesDegenerate Ferromagnetic SemiconductorsDegenerate Antiferromagnetic Semiconductors and Phase SeparationLanthanum ManganitesOther ManganitesSpecific Effects and Theory of Manganites Readership: Advanced graduate students, lecturers and researchers in condensed matter physics, superconductivity and magnetic materials. Keywords:Magnetic Semiconductors;Magnetic Polaron (Ferron);Electronic Phase Separation;Manganites;Colossal Magnetoresistance;Solid State Physics

The physics of transition metal oxides has become a central topic of interest to condensed-matter scientists ever since high temperature superconductivity was discovered in hole-doped cuprates with perovskite-like structures. Although the renewed interest in hole-doped perovskite manganites following the discovery of their colossal magnetoresistance (CMR) properties, began in 1993 about a decade after the discovery of high temperature superconductivity, their first investigation started as early as 1950 and basic theoretical ideas were developed during 1951-1960. Experience in sample preparation and characterization, and in growth of single crystals and epitaxial thin films, gained during the research on high temperature superconductors, and the development of theoretical tools, were very efficiently used in research on CMR manganites. In early nineties it appeared to many condensed matter physicists that although the problem of high temperature superconductivity is a difficult one to solve, a quantitative understanding of CMR phenomena might be well within reach. This book is intended to be an account of the latest developments in the phys ics of CMR manganites. When I planned this book back in 2000, I thought that research on the physics of CMR manganites would be more or less consolidated by the time this would be published. I was obviously very optimistic indeed. We are now in 2003 and we still do not have a quantitative understanding of the central CMR effect. Meanwhile the field has expanded. It is still a very active field of research on both the experimental and theoretical fronts.

This book is devoted to the rapidly developing field of oxide thin-films and heterostructures. Oxide materials combined with atomic-scale precision in a heterostructure exhibit an abundance of macroscopic physical properties involving the strong coupling between the electronic, spin, and structural degrees of freedom, and the interplay between magnetism, ferroelectricity, and conductivity. Recent advances in thin-film deposition and characterization techniques made possible the experimental realization of such oxide heterostructures, promising novel functionalities and device concepts. The book consists of chapters on some of the key innovations in the field over recent years, including strongly correlated oxide heterostructures, magnetoelectric coupling and multiferroic materials, thermoelectric phenomena, and two-dimensional electron gases at oxide interfaces. The book covers the core principles, describes experimental approaches to fabricate and characterize oxide heterostructures, demonstrates new functional properties of these materials, and provides an overview of novel applications.

This book focuses on nanoscale electronic phase separation in a wide class of different materials, especially in strongly correlated electron systems. It features an extensive review of the field of inhomogeneous spin and charge states in condensed matter physics while delivering a topical and timely discussion of a wide range of recent advances in electronic phase separation. It describes the formation of different types of nanoscale ferromagnetic metallic droplets in antiferromagnetically ordered, charge-ordered, or orbitally-ordered insulating matrices, as well as the colossal magnetoresistance effect and tunneling electron transport in the nonmetallic phase-separated state of complex magnetic oxides. It also discusses compounds with spin-state transitions, inhomogeneously phase-separated states in strongly correlated multiband systems, and the electron polaron effect, paying special attention to systems with imperfect Fermi surface-nesting such as chromium alloys, iron-based pnictides, and AA-stacked graphene bilayers. The authors investigate also the formation of order parameter clusters and insulator-superconductor transition in different superconducting systems including bismuth oxides, two-dimensional films in the presence of strong disorder, as well as inhomogeneous Fermi-Bose mixtures in Aharonov-Bohm rings with a superconducting bridge in a topologically nontrivial state. This book is a valuable resource for researchers involved in theoretical and experimental studies of strongly correlated materials, such as magnetic semiconductors, Fermi-Bose mixtures, and twisted bilayer graphene.

This is the first monograph devoted to investigation of the most complex physical processes of soft systems, including a wide class of solutions. It blends modern theoretical understanding and experimental results, proposing new methods and models for the description of several soft systems.