Quantum Tunneling of Magnetization — QTM ’94


Book Description

The first NATO Advanced Workshop on Quantum Tunneling of Magnetization (QTM) was organized and co-directed by Bernard Barbara, Leon Gunther, Nicolas Garcia, and Anthony Leggett and was held from June, 27 through July 1, 1994 in Grenoble and Chichilianne, France. These Proceedings include twenty-nine articles that represent the contributions of the participants in the Workshop. Quantum Tunneling of Magnetization is not only interesting for purely academic reasons. It was pointed out in the review article by L. Gunther in the December, 1990 issue of Physics World, that QTM may be destined to play a significant role within the next two decades in limiting the density of information storage in magnetic systems. Recent advances have indicated that this limitation may well be reached even earlier than first predicted. Furthermore, the number of people who have entered the field of study of QTM during these past few years has increased many fi)ld. The time was therefore opportune to hold a Workshop to bring together for the first time the leading researchers of QTM, both theoretical and experimental, so as to discuss the current status of the field. The most controversial issue at the time of the Workshop was how to establish r.eliable criteria for determining whether experimental results do indeed reveal manifestations of QTM. We believe that much progress was made at the Workshop on this issue.




Macroscopic Quantum Tunneling of the Magnetic Moment


Book Description

This is the first book presenting a coherent theoretical and experimental treatment of the rapidly developing field of macroscopic quantum tunneling of the magnetic moment. The theory is based on the concept of the magnetic instanton and its renormalization by the dissipative environment. The book includes discussions of the tunneling of magnetic moment in small ferromagnetic grains, tunneling of the Ne'el vector in antiferromagnetic grains, quantum nucleation of magnetic domains, and quantum depinning of domain walls. The experimental part collects the majority of recent data that are, or may be, relevant to spin tunneling. Among the topics described are low temperature magnetic relaxation and its interpretation in various systems, experiments on single particles and mesoscopic wires, and resonant spin tunneling in molecular magnets. This study of an important new field in condensed matter physics by two leading contributors to the subject will be of interest to theorists and experimentalists alike.




Lanthanide Single Molecule Magnets


Book Description

This book begins by providing basic information on single-molecule magnets (SMMs), covering the magnetism of lanthanide, the characterization and relaxation dynamics of SMMs and advanced means of studying lanthanide SMMs. It then systematically introduces lanthanide SMMs ranging from mononuclear and dinuclear to polynuclear complexes, classifying them and highlighting those SMMs with high barrier and blocking temperatures – an approach that provides some very valuable indicators for the structural features needed to optimize the contribution of an Ising type spin to a molecular magnet. The final chapter presents some of the newest developments in the lanthanide SMM field, such as the design of multifunctional and stimuli-responsive magnetic materials as well as the anchoring and organization of the SMMs on surfaces. In addition, the crystal structure and magnetic data are clearly presented with a wealth of illustrations in each chapter, helping newcomers and experts alike to better grasp ongoing trends and explore new directions. Jinkui Tang is a professor at Changchun Institute of Applied Chemistry, Chinese Academy of Sciences. Peng Zhang is currently pursuing his PhD at Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, with a specific focus on the molecular magnetism of lanthanide compounds under the supervision of Prof. Jinkui Tang.




Quantum Tunneling of Magnetization


Book Description

The objective of these investigations was to study the magnetic properties of a collection of small magnetic particles or magnetized domains with special attention to detecting and documenting the occurrence of macroscopic quantum tunneling of magnetization. Magnetized small particles are the basic elements used for magnetic storage, and our studies are important from a technological points of view: quantum-mechanical tunneling of the magnetization of small particles sets the ultimate limit on the reliability of magnetic storage and an upper limit on storage density. Experimentally, we succeeded in observing thermally assisted, field-tuned resonant tunneling between quantum spin states in a macroscopic-sized sample of the molecular magnetic material, manganese acetate. The magnetic properties of horse-spleen ferritin were also investigated. Theoretical studies included investigations of tunneling in random magnets, the introduction of the concept of a 'critical state', theoretical studies of antiferromagnetic grains with uncompensated sublattices, and the crossover from antiferromagnetic to ferromagnetic tunneling.




Molecular Magnets


Book Description

This book provides an overview of the physical phenomena discovered in magnetic molecular materials over the last 20 years. It is written by leading scientists having made the most important contributions to this active area of research. The main topics of this book are the principles of quantum tunneling and quantum coherence of single-molecule magnets (SMMs), phenomena which go beyond the physics of individual molecules, such as the collective behavior of arrays of SMMs, the physics of one-dimensional single–chain magnets and magnetism of SMMs grafted on substrates. The potential applications of these physical phenomena to classical and quantum information, communication technologies, and the emerging fields of molecular spintronics and magnetic refrigeration are stressed. The book is written for graduate students, researchers and non-experts in this field of research.




Quantum Tunneling in Complex Systems


Book Description

In the last two decades remarkable progress has been made in understanding and describing tunneling processes in complex systems in terms of classical trajectories. This book introduces recent concepts and achievements with particular emphasis on a dynamical formulation and relations to specific systems in mesoscopic, molecular, and atomic physics. Advanced instanton techniques, e.g. for decay rates and tunnel splittings, are discussed in the first part. The second part covers current developments for wave-packet tunneling in real-time, and the third part describes thermodynamics and dynamical approaches for barrier transmission in statistical, particularly dissipative systems.




Handbook of Spintronics


Book Description

Over two volumes and 1500 pages, the Handbook of Spintronics will cover all aspects of spintronics science and technology, including fundamental physics, materials properties and processing, established and emerging device technology and applications. Comprising 60 chapters from a large international team of leading researchers across academia and industry, the Handbook provides readers with an up-to-date and comprehensive review of this dynamic field of research. The opening chapters focus on the fundamental physical principles of spintronics in metals and semiconductors, including an introduction to spin quantum computing. Materials systems are then considered, with sections on metallic thin films and multilayers, magnetic tunnelling structures, hybrids, magnetic semiconductors and molecular spintronic materials. A separate section reviews the various characterisation methods appropriate to spintronics materials, including STM, spin-polarised photoemission, x-ray diffraction techniques and spin-polarised SEM. The third part of the Handbook contains chapters on the state of the art in device technology and applications, including spin valves, GMR and MTJ devices, MRAM technology, spin transistors and spin logic devices, spin torque devices, spin pumping and spin dynamics and other topics such as spin caloritronics. Each chapter considers the challenges faced by researchers in that area and contains some indications of the direction that future work in the field is likely to take. This reference work will be an essential and long-standing resource for the spintronics community.




The Chemistry of Nanostructured Materials


Book Description

This book is a sequel to the first volume of The Chemistry of Nanostructured Materials. It covers the most exciting developments in the nanostructured materials field for the past five to ten years, with a particular focus on their applications in energy conversion and energy storage. Prominent authors of recognized authority in the field contribute their expertise in the review chapters.




Single-Molecule Magnets


Book Description

Concise overview of synthesis and characterization of single molecule magnets Molecular magnetism is explored as an alternative to conventional solid-state magnetism as the basis for ultrahigh-density memory materials with extremely fast processing speeds. In particular single-molecule magnets (SMM) are in the focus of current research, both because of their intrinsic magnetization properties, as well as because of their potential use in molecular spintronic devices. SMMs are fascinating objects on the example of which one can explain many concepts. Single-Molecule Magnets: Molecular Architectures and Building Blocks for Spintronics starts with a general introduction to single-molecule magnets (SMM), which helps readers to understand the evolution of the field and its future. The following chapters deal with the current synthetic methods leading to SMMs, their magnetic properties and their characterization by methods such as high-field electron paramagnetic resonance, paramagnetic nuclear magnetic resonance, and magnetic circular dichroism. The book closes with an overview of radical-bridged SMMs, which have shown application potential as building blocks for high-density memories. Covers a hot topic – single-molecule magnetism is one of the fastest growing research fields in inorganic chemistry and materials science Provides researchers and newcomers to the field with a solid foundation for their further work Single-Molecule Magnets: Molecular Architectures and Building Blocks for Spintronics will appeal to inorganic chemists, materials scientists, molecular physicists, and electronics engineers interested in the rapidly growing field of study.