Unparalleled in the breadth and depth of its coverage of all important aspects, this book systematically treats the electronic and magnetic properties of stoichiometric and non-stoichiometric ...cobaltites in both ordered and disordered phases. Authored by a pioneer and a rising star in the field, the monograph summarizes, organizes and streamlines the otherwise difficult-to-obtain information on this topic. An introductory chapter sets forth the crystal chemistry of cobalt oxides to lay the groundwork for an understanding of the complex phenomena observed in this materials class. Special emphasis is placed on a comprehensive discussion of cobaltite physical properties in different structural families.Providing a thorough introduction to cobalt oxides from a chemical and physical viewpoint as a basis for understanding their intricacies, this is a must-have for both experienced researchers as well as entrants to the field.
Micromagnetics has been the method of choice to interpret experimental data in the area of microscopic magnetism for several decades. In this article, we show how progress has been made to extend ...this formalism to include thermal and quantum fluctuations in order to describe recent experimental developments in nanoscale magnetism. For experimental systems with constrained dimensions such as nanodots, atomic chains, nanowires, and thin films, topological defects such as solitons, vortices, skyrmions, and monopoles start to play an increasingly important role, all forming novel types of quasiparticles in patterned low-dimensional magnetic systems. We discuss in detail how soliton-antisoliton pairs of opposite chirality form non-uniform energy barriers against thermal fluctuations in nanowires or pillars. As a consequence of their low barrier energy compared to uniform reversal, they limit the thermal stability of perpendicular recording media. For sufficiently short samples, the non-uniform energy barrier continuously merges into the conventional uniform Néel-Brown barrier. Partial formation of chiral domain walls also determines the magnetic properties of granular nanostructured magnets and exchange spring systems. For a long time, the reconciliation between micromagnetics and quantum mechanics has remained an unresolved challenge. Here it is demonstrated how inclusion of Berry's phase in a micromagnetic action allows for a semiclassical quantization of spin systems, a method that is demonstrated by the simple example of an easy-plane spin. This powerful method allows for a description of quantum dynamics of solitons and breathers which in the latter case agrees with the anisotropic spin-½ XYZ-model. The domain wall or soliton chirality plays an important role as it is coupled to the wavevector of the quasiparticle dispersion. We show how this quantum soliton chirality is detected by polarized neutron scattering in one-dimensional quantum antiferromagnets.
A large electric field at the surface of a ferromagnetic metal is expected to appreciably change its electron density. In particular, the metal's intrinsic magnetic properties, which are commonly ...regarded as fixed material constants, will be affected. This requires, however, that the surface has a strong influence on the material's properties, as is the case with ultrathin films. We demonstrated that the magnetocrystalline anisotropy of ordered iron-platinum (FePt) and iron-palladium (FePd) intermetallic compounds can be reversibly modified by an applied electric field when immersed in an electrolyte. A voltage change of -0.6 volts on 2-nanometer-thick films altered the coercivity by -4.5 and +1% in FePt and FePd, respectively. The modification of the magnetic parameters was attributed to a change in the number of unpaired d electrons in response to the applied electric field. Our device structure is general and should be applicable for characterization of other thin-film magnetic systems.
The phenomenon of spin-crossover has a large impact on the physical properties of a solid material, including its colour, magnetic moment, and electrical resistance. Some materials also show a ...structural phase change during the transition. Several practical applications of spin-crossover materials have been demonstrated including display and memory devices, electrical and electroluminescent devices, and MRI contrast agents. Switchable liquid crystals, nanoparticles, and thin films of spin-crossover materials have also been achieved. Spin-Crossover Materials: Properties and Applications presents a comprehensivesurvey of recent developments in spin-crossover research, highlighting the multidisciplinary nature of this rapidly expanding field. Following an introductory chapter which describes the spin-crossover phenomenon and historical development of the field, the book goes on to cover a wide range of topics including * Spin-crossover in mononuclear, polynuclear and polymeric complexes * Structure: function relationships in molecular spin-crossover materials * Charge-transfer-induced spin-transitions * Reversible spin-pairing in crystalline organic radicals * Spin-state switching in solution * Spin-crossover compounds in multifunctional switchable materials and nanotechnology * Physical and theoretical methods for studying spin-crossover materials Spin-Crossover Materials: Properties and Applications is a valuable resource for academic researchers working in the field of spin-crossover materials and topics related to crystal engineering, solid state chemistry and physics, and molecular materials. Postgraduate students will also find this book useful as a comprehensive introduction to the field.
Magnetic ferrofluids (magnetic nanofluids) have received special attention due to their various biomedical applications such as drug delivery and hyperthermia treatment for cancer. The biological ...applications impose some special requirements. For example, the well-known iron oxide ferrofluids become undesirable because their iron atoms are poorly distinguishable from those of hemoglobin. A conceivable solution is to use mixed-ferrites (MFe2O4 where M=Co, Mn, Ni, Zn) to have a range of magnetic properties. These ferrites have attracted special attention because they save time, and because of their low inherent toxicity, ease of synthesis, physical and chemical stabilities and suitable magnetic properties. Based on the importance of ferrite particles in ferrofluids for hyperthermia treatment, this paper gives a summary on the physical concepts of ferrofluids, hyperthermia principal, magnetic properties and synthesis methods of nanosized ferrites.
► This paper gives a suitable summary and literature survey on the ferrofluids. ► Ferrofluids have an important role in biomedicine and our life. ► Ferrofluids include a magnetic core, surfactant and a liquid medium. ► Nano-ferrites' cores are good candidates for hyperthermia purposes. ► They present a suitable heat generation for hyperthermia.
The geometrical structures, relative stabilities, and electronic and magnetic properties of niobium carbon clusters, Nbsub.7Csub.n (n = 1–7), are investigated in this study. Density functional theory ...(DFT) calculations, coupled with the Saunders Kick global search, are conducted to explore the structural properties of Nbsub.7Csub.n (n = 1–7). The results regarding the average binding energy, second-order difference energy, dissociation energy, HOMO-LUMO gap, and chemical hardness highlight the robust stability of Nbsub.7Csub.3. Analysis of the density of states suggests that the molecular orbitals of Nbsub.7Csub.n primarily consist of orbitals from the transition metal Nb, with minimal involvement of C atoms. Spin density and natural population analysis reveal that the total magnetic moment of Nbsub.7Csub.n predominantly resides on the Nb atoms. The contribution of Nb atoms to the total magnetic moment stems mainly from the 4d orbital, followed by the 5p, 5s, and 6s orbitals.
This first introduction to the rapidly growing field of molecular magnetism is written with Masters and PhD students in mind, while postdocs and other newcomers will also find it an extremely useful ...guide. Adopting a clear didactic approach, the authors cover the fundamental concepts, providing many examples and give an overview of the most important techniques and key applications. Although the focus is one lanthanide ions, thus reflecting the current research in the field, the principles and the methods equally apply to other systems. The result is an excellent textbook from both a scientific and pedagogic point of view.
Thermal fluctuations in two-dimensional (2D) isotropy systems at non-zero finite temperatures can destroy the long-range (LR) magnetic order due to the mechanisms addressed in the Mermin-Wanger ...theory. However, the magnetic anisotropy related to spin–orbit coupling (SOC) may stabilize magnetic order in 2D systems. Very recently, 2D FexGeTesub.2 (3 ≤ x ≤ 7) with a high Curie temperature (TC) has not only undergone significant developments in terms of synthetic methods and the control of ferromagnetism (FM), but is also being actively explored for applications in various devices. In this review, we introduce six experimental methods, ten ferromagnetic modulation strategies, and four spintronic devices for 2D FexGeTesub.2 materials. In summary, we outline the challenges and potential research directions in this field.
Writing and Deleting Single Magnetic Skyrmions Romming, Niklas; Hanneken, Christian; Menzel, Matthias ...
Science (American Association for the Advancement of Science),
08/2013, Letnik:
341, Številka:
6146
Journal Article
Recenzirano
Odprti dostop
Topologically nontrivial spin textures have recently been investigated for spintronic applications. Here, we report on an ultrathin magnetic film in which individual skyrmions can be written and ...deleted in a controlled fashion with local spin-polarized currents from a scanning tunneling microscope. An external magnetic field is used to tune the energy landscape, and the temperature is adjusted to prevent thermally activated switching between topologically distinct states. Switching rate and direction can then be controlled by the parameters used for current injection. The creation and annihilation of individual magnetic skyrmions demonstrates the potential for topological charge in future information-storage concepts.
Pure nanoparticles of the rare-earth substituted cobalt ferrites CoRExFe2−xO4 (where RE=Nd, Sm and Gd and x=0.1 and 0.2) were prepared by the chemical co-precipitation method. X-ray diffraction, ...Transmission electron microscopy (TEM), d.c. electrical conductivity, Magnetic hysteresis and Thermal analysis are utilized in order to study the effect of variation in the rare-earth substitution and its impact on particle size, magnetic properties like MS, HC and Curie temperature. The phase identification of the materials by X-ray diffraction reveals the single-phase nature of the materials. The lattice parameter increased with rare-earth content for x≤0.2. The Transmission electron micrographs of Nd-, Sm- and Gd-substituted CoFe2O4 exhibit the particle size 36.1 to 67.8nm ranges. The data of temperature variation of the direct current electrical conductivity showed definite breaks, which corresponds to ferrimagnetic to paramagnetic transitions. The thermoelectric power for all compound are positive over the whole range of temperature. The dielectric constant decreases with frequency and rare-earth content for the prepared samples. The magnetic properties of rare-earth substituted cobalt ferrites showed a definite hysteresis loop at room temperature. The reduction of coercive force, saturation magnetization, ratio MR/MS and magnetic moments may be due to dilution of the magnetic interaction.
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