Metal Organic And Organic Molecular Magnets

Traditionally, magnetic materials have been metals or, if inorganic compounds such as oxides, of continuous lattice type. However, in recent years chemists have synthesized increasing numbers of crystalline solids based on molecular building blocks in the form of coordination and organometallic complexes or purely organic molecules, which exhibit spontaneous magnetization. In striking contrast to conventional magnets, these materials are made from solutions close to room temperature rather than by metallurgical or ceramic methods. This book, which originates from contributions to a Discussion Meeting of The Royal Society of London, brings together many of the leading international practitioners in the field, who survey their own recent work and place it in the context of the wider fields of magnetism and supramolecular chemistry. All aspects of molecular-based magnets are addressed, including synthesis, structure-property relations and physical properties. Contents include details of the characterization of the first purely organic ferromagnet, the synthesis of high coercivity materials and a unique description of new materials with Curie temperatures well above ambient. A coherent survey of this rapidly developing field for the more general reader, Metal-Organic and Organic Molecular Magnets will also be welcomed by researchers and lecturers in materials science and inorganic or solid state chemistry.

Organic materials with extraordinary magnetic properties promise a wide range of light, flexible, and inexpensive alternatives to familiar metal-based magnets. Individual organic molecules with high magnetic moments will be the foundation for design and fabrication of these materials. This book provides a systematic understanding of the structure and properties of organic magnetic molecules. After a summary of the phenomenon of magnetism at the molecular level, it presents a survey of the challenges to theoretical description and evaluation of the magnetic character of open-shell molecules, and an overview of recently developed methods and their successes and shortfalls. Several fields of application, including very strong organic molecular magnets and photo-magnetic switches, are surveyed. Finally, discussions on metal-based materials and simultaneously semiconducting and ferromagnetic extended systems and solids point the way toward future advances. The reader will find a comprehensive discourse on current understanding of magnetic molecules, a thorough survey of computational methods of characterizing known and imagined molecules, simple rules for design of larger magnetic systems, and a guide to opportunities for progress toward organic magnets.

Molecular Magnetism introduces graduates and researchers in chemistry and physics to this newly developed field. This is an exciting area, allowing the development of novel magnetic materials, such as purely organic ferromagnets, to be used in a variety of applications. The book also covers the experimental and theoretical background before discussing the molecular design and synthesis of organic and metal-organic magnetic materials. The properties of various materials, including polyradicals, polymers and other interesting phenomena, such as those associated with photo-induced magnets, are also discussed. Molecular Magnetism is of interest to students and researchers in chemistry, solid state physics, materials science, electronics, photonics and polymer engineering.

Provides an extensive overview of the last three decades of research on the structures and magnetic behaviors of organic and organometallic substances-building a solid foundation for future research into applications of molecular materials based on organic paramagnetic and polymeric systems. Provides the essential body of knowledge for an organically oriented materials science of electronic materials.

This volume highlights the recent advances and state of art in the experimental and theoretical studies of organometallic magnets. A plethora of organic ligands such as Mannich-base derivatives, redox-active chromophores, cyanides, Schiff base among others are used to coordinate to 3d transition metals, 4f lanthanides and 5f actinides to design the molecular magnets. Deep analysis of the coordination sphere symmetry, electronic distribution, luminescence are investigated to perform magneto-structural correlation leading to a better understanding of the magnetic properties. Furthermore, the rationalization of the magnetic behavior can be reached using ab initio calculations. The multiple applications that these molecular magnets offer could revolutionize the high-density data storage, spintronics and quantum computing technologies. This volume provides a discussion of these topics from leading international experts and will be a useful reference for researchers working in this field.

We nave measured the high-field magnetization of a number of Ni-based metal-organic molecular magnets. These materials are self-assembly coordination polymers formed from transition metal ions and organic ligands. The chemistry of the compounds is versatile allowing many structures with different magnetic properties to be formed. These studies follow on from previous measurements of the Cu-based analogues in which we showed it was possible to extract the exchange parameters of low-dimensional magnets using pulsed magnetic fields. In our recent experiments we have investigated the compound (Ni(HF2)(pyz)2)PF6, where pyz = pyrazine, and the Ni-ions are linked in a quasi-two-dimensional (Q2D) square lattice via the pyrazine molecules, with the layers held together by HF2 ligands. We also investigated Ni(NCS)2(pyzdo)2, where pyzdo = pyrazine dioxide. The samples are grown at Eastern Washington University using techniques described elsewhere. Measurements are performed at the pulsed magnetic field laboratory in Los Alamos. The magnetization of powdered samples is determined using a compensated coil magnetometer in a 65 T short pulse magnet. Temperatures as low as 500 mK are achievable using a 3He cryostat. The main figure shows the magnetization of the spin-1 [Ni(HF2)(pyz)2]PF6 compound at 1.43 K. The magnetization rises slowly at first, achieving a rounded saturation whose midpoint is around 19 T.A small anomaly is also seen in the susceptibility at low fields (≈3 T), which might be attributed to a spin-flop transition. In contrast, the spin-1/2 [Cu(HF2)(pyz)2]PF6 measured previously has a saturation magnetization of 35.5 T and a strongly concave form of M(B) below this field. This latter compound was shown to be a good example of a Q2D Heisenberg antiferromagnet with the strong exchange coupling (J{sub 2D} = 12.4 K, J{sub {perpendicular}}/J{sub 2D} ≈ 10−2) directed along the Cu-pyz-Cu directions. The structure of the two compounds is similar, but in the case of the Cu-compound the Cu-Cu pathways are linear, whereas in the Ni-compound they are kinked. The pulsed-field data combined with information from temperature-dependent susceptibility, muon-spin rotation, electron-spin resonance and ligand-field calculations suggest that, far from being magnetically Q2D, the Ni-compound is fairly one-dimensional with the dominant exchange (J{sub 1D} = 3.1 K and J{sub {perpendicular}}/J{sub 1D} = 0.63) directed along the Ni-FHF-Ni direction. Ni(NCS)2(pyzdo)2 was also investigated. Previous ultra-high field measurements using the 100 T magnet have shown that this compound has a saturation field close to 80 T. The purpose of the present studies is to map out the phase diagram of this material at mid-range fields. The data are shown in the inset to the figure. This continuing project probes the ability of organic ligands to mediate magnetic exchange, the link between structure, dimensionality and bulk magnetic properties, as well as the role of spin number in quantum magnets. Ultimately the investigations aim to determine to what extent it is possible to produce self-assembly molecular materials with tailor-made magnetic characteristics.

Carbon Based Magnetism is the most complete, detailed, and accurate guide on the magnetism of carbon, the main element of living creatures. Written by the leading experts in the field, the book provides a comprehensive review of relevant experimental data and theoretical concepts related to the magnetism of metal-free carbon systems. These systems include carbon based compounds, namely organic radical magnetic systems, and magnetic materials based on carbon structures. The aim is to advance the understanding of the fundamental properties of carbon. This volume discusses all major modern hypotheses on the physical nature of magnetic ordering in carbon systems. The first chapters deal with magnetic ordering mechanisms in p-electron systems as well as molecular magnets with spins residing only in p-orbitals. The following chapters explore the magnetic properties of pure carbon, with particular emphasis on nanosized carbon systems with closed boundary (fullerenes and nanotubes) and with open boundary (structures with edge-localized magnetic states). The remaining chapters focus on newer topics: experimental observation and theoretical models for magnetic ordering above room temperature in pure carbon. The book also includes twenty three review articles that summarize the most significant recent and ongoing exciting scientific developments and provide the explanation. It also highlights some problems that have yet to be solved and points out new avenues for research. This book will appeal to physicists, chemists and biologists. The most complete, detailed, and accurate Guide in the magnetism of carbon Dynamically written by the leading experts Deals with recent scientific highlights Gathers together chemists and physicists, theoreticians and experimentalists Unified treatment rather than a series of individually authored papers Description of genuine organic molecular ferromagnets Unique description of new carbon materials with Curie temperatures well above ambient.