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2017 | Book

The Basis of Nanomagnetism Read chapter Read first chapter

Principles of Nanomagnetism

Author: Alberto P. Guimarães

Publisher: Springer International Publishing

Book Series : NanoScience and Technology

Part of: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik"

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About this book

The second edition of this book on nanomagnetism presents the basics and latest studies of low-dimensional magnetic nano-objects. It highlights the intriguing properties of nanomagnetic objects, such as thin films, nanoparticles, nanowires, nanotubes, nanodisks and nanorings as well as novel phenomena like spin currents. It also describes how nanomagnetism was an important factor in the rapid evolution of high-density magnetic recording and is developing into a decisive element of spintronics. Further, it presents a number of biomedical applications. With exercises and solutions, it serves as a graduate textbook.

Table of Contents

Frontmatter
Chapter 1. The Basis of Nanomagnetism
Abstract
The exchange length and the magnetic domain wall width are some of the characteristic lengths that are more relevant to the magnetic properties. The shape of the density of electronic states curve is also dependent on the dimensionality of the samples.
Alberto P. Guimarães
Chapter 2. Magnetic Domains
Abstract
The existence of magnetic domains arises from the action of several interactions present in magnetic materials, mainly exchange, anisotropy, and dipolar. This chapter deals with some properties of magnetic domains and magnetic domain walls, including the motion of these walls under an applied magnetic field. A short introduction to micromagnetism, an approach to the study of magnetic materials that considers these materials as a continuum, is also given, as well as the origin of some of the characteristic lengths in magnetism.
Alberto P. Guimarães
Chapter 3. Magnetism of Small Particles
Abstract
Magnetic nanoparticles are important physical systems, relevant for many applications and, in many cases, the starting point of fundamental developments in nanomagnetism. The Stoner–Wohlfarth theory, discussed in this chapter, represents a milestone in the process of understanding nanoparticle magnetism. This theory describes the magnetic properties of ellipsoidal magnetic particles, including the conditions for the homogeneous reversal of their magnetization under applied magnetic field. Magnetic nanoparticles present spin arrangements that may be single domain, vortex state, or multidomain, with their magnetic behavior depending on the spin configuration. The critical diameters for these configurations can be derived in an approximate form. Nanoparticles in the smaller range of diameters do not behave as stable magnets, exhibiting the phenomenon of superparamagnetism .
Alberto P. Guimarães
Chapter 4. Magnetism of Thin Films and Multilayers
Abstract
Magnetic thin films are the most extensively studied magnetic system with nanoscale dimensions. The study of the properties of magnetic thin films has made possible the development of film media used in magnetic hard disks and the progress in reading heads. In this chapter, these properties are discussed, including the anisotropy of thin films. Multilayers prepared from thin films give rise to a wealth of properties, arising in particular, from the interaction between the magnetic layers, i.e., the interlayer exchange coupling. The phenomenon of exchange bias, discovered in granular materials, has also been systematically studied in thin films, and finds important applications.
Alberto P. Guimarães
Chapter 5. Magnetotransport and Spin CurrentSpin current Effects
Abstract
In this chapter, a brief account of some phenomena resulting from the interplay of the magnetization of a sample and the spin-polarized currents, the physical basis of spin electronics, or Spintronics will be given. These include the giant magnetoresistance and tunnel magnetoresistance effects. Simple models for the description of these effects are presented. Other spin current effects are discussed: the spin- induced, or spin transfer torque, the spin Hall effect, spin pumping, and spin thermal effects.
Alberto P. Guimarães
Chapter 6. Magnetism of Nanodisks, Nanorings, Nanowires, and Nanotubes
Abstract
This chapter contains a brief survey of the remarkable magnetic properties of low-dimensional magnetic objects such as nanodisks, nanorings, nanotubes, and nanowires. These nanoscale systems have been intensely studied in the last years, not only because of these properties, but also for their enormous potential for high-density information storage and other applications. Nanodisks and nanorings are promising as elements of bit-patterned magnetic recording systems, nanotubes and nanowires, among other applications, can store and process information through the motion of magnetic domain walls
Alberto P. Guimarães
Chapter 7. Magnetic Recording
Abstract
Magnetic storage is the most important technology for data recording and has progressed very rapidly in the last half century. Although it has reached a high level of refinement, it is still evolving and experimenting new proposals. Random access magnetic memories have been developed or proposed, using the magnetization states of magnetic nanodisks and nanorings; other solutions include the encoding of information onto a string of magnetic domains, or of skyrmions, in magnetic strips and nanowires. This chapter describes the main concepts behind magnetic recording, aspects of the evolution of the recording technologies, and the current challenges faced by this field to continue its capacity expansion.
Alberto P. Guimarães
Backmatter
Metadata
Title
Principles of Nanomagnetism
Author
Alberto P. Guimarães
Copyright Year
2017
Electronic ISBN
978-3-319-59409-5
Print ISBN
978-3-319-59408-8
DOI
https://doi.org/10.1007/978-3-319-59409-5

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