Physics
Magnetic Materials
Magnetic materials are substances that can be magnetized or attracted by a magnetic field. They are characterized by their ability to produce a magnetic field and to attract or repel other magnetic materials. Common examples of magnetic materials include iron, nickel, and cobalt, as well as certain alloys and compounds.
Written by Perlego with AI-assistance
Related key terms
1 of 5
9 Key excerpts on "Magnetic Materials"
eBook - PDFFundamentals of Materials Science and Engineering
An Integrated Approach
- William D. Callister, Jr., David G. Rethwisch(Authors)
- 2016(Publication Date)
- Wiley(Publisher)
6. Note the distinctive magnetic characteristics for both soft and hard Magnetic Materials. 7. Describe the phenomenon of superconductivity. Magnetism—the phenomenon by which materials exert an attractive or repulsive force or influence on other materials—has been known for thousands of years. However, the underlying principles and mechanisms that explain magnetic phenomena are complex and subtle, and their understanding has eluded scientists until relatively recent times. Many modern technological devices rely on magnetism and Magnetic Materials, including electrical power generators and transformers, electric motors, radio, television, tele- phones, computers, and components of sound and video reproduction systems. Iron, some steels, and the naturally occurring mineral lodestone are well-known examples of materials that exhibit magnetic properties. Not so familiar, however, is the fact that all substances are influenced to one degree or another by the presence of a magnetic field. This chapter provides a brief description of the origin of magnetic fields and discusses magnetic field vectors and magnetic parameters; diamagnetism, paramagnetism, ferromagnetism, and ferrimagnetism; different Magnetic Materials; and superconductivity. Magnetic Dipoles Magnetic forces are generated by moving electrically charged particles; these magnetic forces are in addition to any electrostatic forces that may exist. Often it is convenient to think of magnetic forces in terms of fields. Imaginary lines of force may be drawn to indicate the direction of the force at positions in the vicinity of the field source. The magnetic field distributions as indicated by lines of force are shown for a current loop and a bar magnet in Figure 18.1. Magnetic dipoles are found to exist in Magnetic Materials and in some respects are analogous to electric dipoles (Section 12.19).
- Donald Askeland, Wendelin Wright, Donald Askeland(Authors)
- 2020(Publication Date)
- Cengage Learning EMEA(Publisher)
Magnetic Materials C H A P T E R 20 Have You Ever Wondered? ● What affects the “lifting strength” of a magnet? ● What are “soft” and “hard” Magnetic Materials? ● Are there “nonmagnetic” materials? ● Are there materials that develop mechanical strain upon the application of a magnetic field? Chapter Learning Objectives The key objectives of this chapter are to ● Define the terms ferromagnetic, ferrimagnetic, paramagnetic, diamagnetic, anti-ferromagnetic, and superparamagnetic. ● Explain the physical basis for the magnetic behavior of elements based on electron spin and orbital motion of electrons around the nucleus. ● Calculate magnetic field and inductance. ● Define the terms magnetic permeability of vacuum, relative permeability of a material, and magnetic susceptibility. ● Describe the movement of domains in a magnetic field and the accompanying change in magnetization due to an increase in the applied magnetic field. ● Identify saturation magnetization, remanance, and coercive field on ferromagnetic hysteresis loops. E very material in the world responds to the presence of a magnetic field. Magnetic Materials are used to construct such things as electrical motors, generators, and transformers. Much of data storage technology (computer hard disks, computer disks, and the like) is based on magnetic particles. Magnetic Materials are also used in loudspeakers, microphones, land-line telephones, and tape - based video recorders. Magnetic Materials, such as iron oxide (Fe 3 O 4 ) particles, are Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
eBook - PDFElectrons, Neutrons and Protons in Engineering
A Study of Engineering Materials and Processes Whose Characteristics May Be Explained by Considering the Behavior of Small Particles When Grouped Into Systems Such as Nuclei, Atoms, Gases, and Crystals
- J. R. Eaton(Author)
- 2013(Publication Date)
- Pergamon(Publisher)
CHAPTER 20 MAGNETIC PROPERTIES OF MATERIALS Magnetic Materials find a wide range of application in science and industry, being used in the construction of transformers, generators, relays, loud speakers, electrical instruments and many other devices. An estimated hundred million dollars'-worth of magnetic steel is used each year by the electrical industry, and the power losses occasioned by their use in operating equipment cost perhaps two hundred million dollars per year. It is at once obvious that magnetic ma-terials are of great economic significance. The early developments in Magnetic Materials came about as a result of the intuition and experimentation of the metallurgists, who made advances with but little theoretical guidance. The first scientific studies in this field were at-tempts to find theories to explain the behavior of the materials which had been in existence for some time. As the theory developed, means of improving exist-ing materials soon became evident; and with increased theoretical knowledge, new types of materials were predicted and eventually produced. As a result of theoretical and experimental advances, Magnetic Materials are available today which have characteristics far superior to those which were known before theoretical study had made significant progress. 20.1. T H E O R I G I N OF THE M A G N E T I C BEHAVIOR OF MATERIALS If a magnetic intensity H exists in free space a flux-density B will be observed such that B 0 = μ 0 Η (20.1) where μ 0 is the permeability of free space. If the same intensity //exists in a material of permeability μ, the flux density will be B = μΗ (20.2) where B may be greater or less than B 0 · It is sometimes desirable to rewrite Equation (20.2) in the form B = μ 0 Η + (μ -μ 0 )Η. (20.3) 388 MAGNETIC PROPERTIES OF MATERIALS 389 The term (μ — μ 0 )Η, known as the intensity of magnetization, may be attribu-ted to the response of the material to the applied magnetic intensity.
- Wei Gao, Zhengwei Li;Nigel Sammes;;(Authors)
- 2011(Publication Date)
- WSPC(Publisher)
Magnetic Properties and Materials 159 make magnets was to rub steel with a lodestone or another magnet, until the electromagnetic field was discovered by Hans Oersted in ~1820. It was not generally recognised that the development of new Magnetic Materials was also responsible for the revolutionary developments in modern electric and electronic industries. Magnetic Materials play very important roles in almost all the equipment that use modern technology, for example, ferrite magnets in TV, memory cores in computers, permanent magnets in motors, superconducting magnets in particle accelerators, to name a few. We would have no audio/video equipment without suitable Magnetic Materials. Magnetic Materials are functional materials, but sometimes they are also used in large quantities (many tons) such as for the core materials in power transformers. Like semiconductor materials, the quality of mag-netic materials strongly influences the performance, efficiency, energy consumption, size and reliability of electric and electronic equipment. Great progress has been made in quality improvement of the Magnetic Materials in the recent years. Fig. 6.1 shows the progress in permanent Magnetic Materials during the last 100 years. Fig. 6.1 Progress in Magnetic Materials measured by the maximum energy products ( BH ) max . Year 1900 1980 1940 1960 2000 1920 100 300 400 200 500 (BH) max (kJ/m 3 ) Steel Alnico SmCo 5 SmCo 7.5 Nd -Fe -B 160 Introduction to Electronic Materials for Engineers 6.2 Fundamentals 6.2.1 Magnetic flux and permeability Compare an electric circuit with a magnetic circuit (Fig. 6.2): if a volt-age, V , is applied to a conductor, the current I that flows in it is related to the conductivity σ of the material: Fig. 6.2 Analogy between (a) electric circuit and (b) magnetic circuit. V = I · R, R = ρ ⋅ l/A = l/ ( σ ⋅ A ), V = ( I/A )( l/ σ ), σ = ( I/A ) × ( 1/E ), (6.1) E = V/l, σ = J/E = (current density)/(electrical field).
eBook - PDF- Md Nazoor Khan, Simanchala Panigrahi(Authors)
- 2017(Publication Date)
- Cambridge University Press(Publisher)
5 Magnetic Properties of Materials 5.1 Introduction In contradiction to our day-to-day spoken language, without exception, scientifically, all materials are magnetic; there are no materials that can actually be called non-magnetic. The material which has the ability to respond to an externally applied magnetic field or can be magnetized is called a magnetic material. All materials can be magnetized to a varying degree of magnetization. 5.2 Magnetic Parameters The terms which can be used to describe the concepts of magnetism are called magnetic parameters. The important magnetic parameters that are used to characterize the magnetic behaviour of materials are enumerated here. i. Magnetic dipole moment µ m : Any two equal and opposite magnetic poles separated by a small distance constitute a magnetic dipole. If pole strength of the dipole is m [Ampere × meter] and the distance from the south pole to the north pole is , the magnetic dipole moment µ m of a magnetic dipole is defined as µ = m m (5.1) The magnetic dipole moment µ m is a vector quantity, the direction being from the south pole to the north pole. The magnetic dipole moment of the current carrying loop µ m is also given as µ = m nia (5.2) 120 Principles of Engineering Physics 2 where i is the current flowing in a loop of n turns having area a . Here direction of the magnetic dipole moment µ m may be found out by applying the screw rule: (i) Place the screw at the centre of the loop perpendicular to the plane of the loop. (ii) Rotate the screw in the direction of the current flowing in the loop. (iii) The direction of linear motion of the screw is the direction of the magnetic moment of the current- carrying loop. The torque t experienced by a magnetic dipole placed in a magnetic field of induction B is given as τ µ = × m B (5.3) ii.
eBook - PDF- Patrick M. Woodward, Pavel Karen, John S. O. Evans, Thomas Vogt(Authors)
- 2021(Publication Date)
- Cambridge University Press(Publisher)
9 Magnetic Materials 9.1 Magnetic Materials and Their Applications While most people are familiar with the concept of a magnet, many do not realize the ubiquity of Magnetic Materials in our everyday lives. Every electric motor contains a ferro- or ferrimagnet. So does every headphone, loudspeaker, and power-supply transformer. Magnetic card strips contain ferrimagnetic γ-Fe 2 O 3 . The old technology of tape recording used γ-Fe 2 O 3 or ferromagnetic CrO 2 . Hard disks in computers have recording platters coated with ferromagnetic alloys patterned on a nanometer scale. The fundamental origin of magnetism can be traced back to the movement of an electrical charge. This can be the flow of current in an electrical circuit or, as in the solids we’ll discuss, due to the quantum-mechanical properties of electrons in atoms. In this chapter we first introduce some of the key physical concepts of magnetism and define some of the quantities involved. We will discuss how to understand concepts such as diamagnetism and paramagnet- ism of isolated atoms and their assemblies. We will then move on to study the origins of cooperative phenomena such as antiferromagnetism, ferromagnetism, and ferrimagnetism and how these can be controlled and exploited in functional materials. It is perhaps worth noting at the outset that magnetism is an area where we’ll encounter unfamiliar units and where it’s often more convenient to work in non-standard units, the so-called CGSem units, than the standard SI system. We’ll generally adopt SI but will choose to list the alternative CGSem units in situations where they’re most commonly encountered in the literature. 9.2 Physics of Magnetism 9.2.1 Bar Magnets and Atomic Magnets Most people are familiar with the everyday properties of bar magnets from childhood toys and school science experiments. We know that they send magnetic field as though emanating 349
- Robert J. Naumann(Author)
- 2008(Publication Date)
- CRC Press(Publisher)
25 Magnetism and Magnetic Materials Magnetism may be thought of as electricity in motion. It is actually a relativistic effect of moving charges according to Einstein ’ s special theory of relativity. One observes a mag-netic fi eld in a reference frame that electrons are fl owing through, but in a reference frame that moves with the electrons, one observes only an electric fi eld. Natural ferromagnets in the form of loadstones were known to the ancient Chinese who used them for navigation. Hans Christian Ørsted was the fi rst person to connect magnetism with electricity when he noticed that a fl owing current in fl uenced a compass needle. Magnetic Materials continue to play an ever increasing role in our modern technical society. For example, the recent discovery of low-cost iron-neodymium-boron magnets has made it possible to build highly ef fi cient permanent magnet motors that are used in hybrid vehicles and will be used in future electric vehicles. Another example is the continued development of magnetic storage media, which have extended hard drive storage capaci-ties far beyond what anyone would have expected a decade ago and have made high performance computers affordable to almost everyone. In order to understand how these materials function, we need to start with some basic principles. 25.1 Basic Relationships Just as the capacitance was increased when a dielectric with polarization P was placed between the plates of a capacitor, the magnetic fi eld in, or in the vicinity of, a material is altered by the magnetization M of the material. By analogy with the electric fi eld case in which we wrote D ¼ « E , we can write for the case of the magnetism B ¼ m H , where H is the applied magnetic fi eld (A = m), B is the resulting fl ux density (V s = m 2 ¼ Wb = m 2 ¼ T), and m is the permeability of the medium.
eBook - PDF- Wenceslao González-Viñas, Héctor L. Mancini(Authors)
- 2015(Publication Date)
- Princeton University Press(Publisher)
Magnetic Materials AND DIELECTRICS 57 H = 1 µ B = 1 µ 0 µ r B, where is the permittivity and µ is the permeability. 2 In anisotropic media these are tensors 3 and the relative permitivity r and permeability µ r may depend on E and B ; their value is 1 in vacuum. Other parameters can be defined, in particular, the susceptibility χ and the electrical susceptibility χ e , which indicate how the polarizations change with respect to the fields. The result? Different properties of magnetic or electrical materials can be related to the behaviors of their susceptibilities: P = 0 χ e E, M = χ H. As is well known, there are no magnetic monopoles. The sources of the magnetic field are electrical currents and intrinsic magnetic dipoles. Inside matter, these sources are, first, currents generated by electron movement and thus connected to angular momentum and, second, the intrinsic magnetic moments of the electrons and the atomic nucleus (and hence their spins). An electron’s magnetic moment caused by its spin is the Bohr magneton µ B = e ¯ h/2m e . Magnetic Materials belong to three categories: paramagnets, diamagnets, and ferro- magnets. Paramagnets and diamagnets do not show any magnetization in zero field. The interaction between magnetic dipoles gives ferroMagnetic Materials, where it is possible to obtain a nonzero magnetization without an applied field. Paramagnets and ferromagnets are made of permanent microscopic magnetic dipoles. But diamagnets are a response to external fields in materials having molecules with a zero magnetic dipolar moment. The magnetization is the sum of a region’s magnetic dipole moments. 6.1 DIAMAGNETISM AND PARAMAGNETISM ParaMagnetic Materials have a small positive magnetic susceptibility χ . This stems from the tiny interaction between material magnetic dipoles.
eBook - PDF- Pradeep Fulay, Jung-Kun Lee(Authors)
- 2016(Publication Date)
- CRC Press(Publisher)
473 11 Magnetic Materials 11.1 INTRODUCTION The word magnet has its origin in a magnetic material known as magnetite, which is a form of iron oxide or lodestone used as a magnetic compass. Lodestone was mined in the province of Magnesia. It is believed that among the minerals found in Magnesia (a part of Macedonia), magnesium carbon-ate was white, manganese dioxide was brown, and the third magnetite was black iron oxide. The magnetite was probably the first material known to be magnetic. As we will see, in reality, all materials in this world are magnetic, that is, they respond to mag-netic fields in some fashion. One objective of this chapter is to introduce the fundamental concepts related to Magnetic Materials. In this regard, we will explore the origin of magnetism in materials. We will define different types of magnetism in materials that include ferromagnetic and ferrimag-netic materials. The second objective is to explore different technologies based on the use of mag-netic materials, including those used in information storage (e.g., magnetic hard disks). We will also briefly mention materials called multiferroics . These materials simultaneously exhibit two or more switchable properties, such as ferroelectric and ferromagnetic behaviors. Since the origins of the ferroelectricity and the ferromagnetism are different, there is a huge amount of interest in the basic science of multiferroics. Also, the magnetically tunable dielectric polarization and the electrically tunable magnetization have a great potential to offer a new paradigm of the device physics. Most concepts regarding Magnetic Materials and technologies would be better followed if you have already learned the basics of linear dielectric materials and ferroelectric materials from Chapter 10. You would start to recognize that many of the equations we would deal with here for Magnetic Materials are very similar to those used for ferroelectrics.
Index pages curate the most relevant extracts from our library of academic textbooks. They’ve been created using an in-house natural language model (NLM), each adding context and meaning to key research topics.
