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Recent progress on the theoretical studies of fast magnetization reversal of Stoner particles is reviewed. The following results are discussed: (1) The Stoner–Wohlfarth (SW) limit becomes exact when the damping constant is infinitely large. Under the limit, magnetization moves along the steepest energy descent path. (2) For a given magnetic anisotropy, there is a critical damping constant, above which...
Nanoclusters, aggregates of a few tens to millions of atoms or molecules, have been extensively studied over the past decades. Core–shell nanoclusters have received increasing attention because of their tunable physical and chemical properties through controlling chemical composition and relative sizes of core and shell. The magnetic core–shell nanoclusters are of particular interests because these...
The fabrication, structure, and magnetism of a variety of designed nanostructures are reviewed, from self-assembled thin-film structures and magnetic surface alloys to core–shell nanoparticles and clusters embedded in bulk matrices. The integration of clusters and other nanoscale building blocks in complex two- and three-dimensional nanostructures leads to new physics and new applications. Some explicitly...
Clathrates are materials containing closed polyhedral cages stacked to form crystalline frameworks. With Si, Ge, and Sn atoms populating these frameworks, a wide variety of electronic and vibrational properties can be produced in these materials, by substitution upon framework sites or through incorporation of ions in cage-center positions. Commonly formed structures include the type I, type II, and...
Neutron scattering is a comprehensive tool for condensed matter research. After a brief description of the interaction of neutrons with matter, the usefulness of neutrons to probe the physical properties of magnetic materials is illustrated using examples taken from different research areas. Then a description of the crystal structure investigation, including in situ and time-resolved studies is given...
Extrinsic control mechanisms of the interface magnetization in exchange bias heterostructures are reviewed. Experimental progress in the realization of adjustable exchange bias is discussed with special emphasis on electrically tunable exchange bias fields in magnetic thin film heterostructures. Current experimental attempts and concepts of electrically controlled exchange bias exploit magnetic bilayer...
Recently, much attention has been focused on new concepts of highly integrated spintronics devices based on magnetic domain walls driven by a spin-polarized current. However, several fundamental questions must be answered before the technology can be considered as feasible. This review covers the current understanding of DW propagation along sub-micronic size wires with ultra-thin films having perpendicular...
Spintronics describes the concept of attempting to use both the charge and the spin on the electron in microelectronic devices [1, 2]. One of the most highly sought after functionalities in microelectronics is non-volatility, i.e. the ability to retain memory even when power is removed. This is particularly true as the popularity of mobile electronic communication and computing devices grows. In principle,...
Bit-patterned recording shows potential as a route to thermally stable data recording at densities greater than 1 Tbit/in2, provided that a number of challenging requirements can be met. Micromagnetic modeling of the write process shows that high write-field gradient (>350 Oe/nm) and tight tolerances on island fabrication and write synchronization (both in the range of ∼1 nm sigma) are required...
The magnetic microstructure and magnetization processes of nanostructured materials are reviewed in a phenomenological way, mainly based on domain observation by magneto-optical Kerr microscopy. This covers nanocrystalline soft magnetic ribbons and films as well as nanostructured hard magnetic materials. For comparison also the domain structure in coarse-grained material and amorphous ribbons are...
Exchange-coupled nanocomposite magnets are a new type of permanent magnetic materials. Large amounts of theoretical and experimental research have been carried out in the past two decades in understanding the inter-phase exchange interactions and in processing bulk nanocomposite magnets with enhanced energy products. This chapter reviews recent advancements in both the fundamental research and the...
This chapter reviews the development of SmCo-type magnets over the last 40 years. First, the physical metallurgy and crystal structures are considered; then the focus is on the recent developments in high-temperature Sm(CobalFewCuxZry)z magnets suitable for operation temperatures up to 500°C. It is...
Reduction of the grain size to less than 20 nm has provided major advances in soft magnetic materials performance, including reduced core losses and coercivities. These promising results have stimulated research efforts, worldwide, in the areas of nanocrystalline alloy design, alloy processing, materials performance evaluation, and transition to various applications. This chapter presents recent advances...
Giant magnetically induced strain up to 50 times larger compared to the strain of giant magnetostriction was observed in some Heusler alloys, particularly in Ni–Mn–Ga. In analogy with the shape memory phenomenon this effect was called magnetic shape memory effect. The effect includes two different phenomena: a magnetically induced structural phase transformation (usually a martensitic transformation)...
A brief review for magnetocaloric effect (MCE), including its potential application to magnetic refrigeration and the corresponding magnetic materials, has been given. Focuses are recent progresses in the exploration of magnetocaloric materials which exhibit a first-order phase transition, thus a giant MCE. Special issues such as proper approaches to determine the MCE associated with the first-order...
This chapter contains both the description of advanced spintronic devices for logic and memory applications and the synthesis and characterization of some new magnetic materials that would lead to new paradigms in spintronics. The first part gives a brief introduction to spintronics and its history. First-generation spintronics has entered the mainstream of information technology through its utilization...
$${\rm CrO}_2$$ is a remarkable ferromagnetic material that is simultaneously an excellent metal for majority spin electrons and an insulator for minority spin electrons [1–3]. For this reason, $${\rm CrO}_2$$ is called a half-metal, and in fact, it is the only one experimentally demonstrated [4–6]. Because of this, $${\rm CrO}_2$$ has received considerable interest for spintronic applications...
This chapter reviews recent studies of chemically synthesized FePt and related nanoparticles. Various methods for synthesizing the nanoparticles and controlling their shape are described. Thermal effects in nanoparticles near the superparamagneticsuperparamagnetic limit are discussed. Some of the methods for reducing sintered grainsintered grain growth during annealing to obtain the L10 phase are...
We review some recent advances in the field of magnetic manipulation techniques, with particular emphasis on the manipulation of mixed suspensions of magnetic and nonmagnetic colloidal particles. We will first discuss the theoretical framework for describing magnetic forces exerted on particles within fluid suspensions. We will then make a distinction between particle systems that are highly dependent...
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