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6.1.4 Magnetization
6.1.4 Magnetization
Published: 2012/10/18
Channel: jg394
Methods of Magnetisation and Demagnetisation
Methods of Magnetisation and Demagnetisation
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What is Magnetization and Magnetic Intensity?
What is Magnetization and Magnetic Intensity?
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Atomic Origins of Magnetization {Texas A&M: Intro to Materials}
Atomic Origins of Magnetization {Texas A&M: Intro to Materials}
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Magnetization with Electricity
Magnetization with Electricity
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Physics Matter & Magnetism part 17 (Magnetization) CBSE class 12
Physics Matter & Magnetism part 17 (Magnetization) CBSE class 12
Published: 2012/09/05
Channel: ExamFear Education
Origin of Magnetization in Magnetic Materials {Texas A&M: Intro to Materials (MSEN 201)}
Origin of Magnetization in Magnetic Materials {Texas A&M: Intro to Materials (MSEN 201)}
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Joseph Vincent - Magnetize (Official Video)
Joseph Vincent - Magnetize (Official Video)
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Magnetization Meaning
Magnetization Meaning
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Magnetization
Magnetization
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Channel: WikiAudio
Different Magnetization Methods
Different Magnetization Methods
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Channel: SuperMagnetMan
How to make a device that will magnetize anything
How to make a device that will magnetize anything
Published: 2010/02/28
Channel: kazesamurai1000
Magnetizing Magnets With An Industrial Magnetizer #1
Magnetizing Magnets With An Industrial Magnetizer #1
Published: 2014/07/07
Channel: ApexMagnets
Magnetic Susceptibility And Magnetizing  Intensity
Magnetic Susceptibility And Magnetizing Intensity
Published: 2015/06/18
Channel: VIKRAM SINGH PHYSICS
How to : Magnetize a Screwdriver
How to : Magnetize a Screwdriver
Published: 2014/02/15
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New Imperial Knight Titan - Magnetization Tutorial
New Imperial Knight Titan - Magnetization Tutorial
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512 - Magnetization by domain walls motion.
512 - Magnetization by domain walls motion.
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Learn How to Magnetize Your Miniatures!
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MAGNETIZING Secrets - How to magnetize your army! | HD
MAGNETIZING Secrets - How to magnetize your army! | HD
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magnetization process of small block neodymium magnet
magnetization process of small block neodymium magnet
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Channel: China Magnets Source Material Limited
Introducing MRI: Introduction to NMR -- Transverse Component Magnetization (6 of 56)
Introducing MRI: Introduction to NMR -- Transverse Component Magnetization (6 of 56)
Published: 2014/09/23
Channel: Albert Einstein College of Medicine
Introducing MRI: Transverse Magnetization Relaxation (10 of 56)
Introducing MRI: Transverse Magnetization Relaxation (10 of 56)
Published: 2014/09/23
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Joseph Vincent - Magnetize (LYRICS)
Joseph Vincent - Magnetize (LYRICS)
Published: 2017/01/04
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Garbage - Magnetized
Published: 2016/10/05
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DC Motor
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Tom Odell - Magnetised (Official Video)
Tom Odell - Magnetised (Official Video)
Published: 2016/04/15
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Magnetizing Inrush Current of Transformer
Magnetizing Inrush Current of Transformer
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Kingdom Death Magnetization
Kingdom Death Magnetization
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Wraithguard Wraithblade Magnetization Tutorial | Modeling | TechWarPainting
Wraithguard Wraithblade Magnetization Tutorial | Modeling | TechWarPainting
Published: 2013/06/09
Channel: Technose
Magnetized Mullet Challenge
Magnetized Mullet Challenge
Published: 2016/03/17
Channel: Good Mythical Morning
Axial vs Diamagnetic Magnetization Compared
Axial vs Diamagnetic Magnetization Compared
Published: 2016/06/15
Channel: ApexMagnets
Warhammer 40K Haruspex/Exocrine assembly and magnetization
Warhammer 40K Haruspex/Exocrine assembly and magnetization
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9.2 - Relaxation of nuclear magnetization
9.2 - Relaxation of nuclear magnetization
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Magnetizing new Space Marine Tactical Squad
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Warlord Titan- assembly and magnetization
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MPI Tutorials - Coil Magnetization
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Eldar Wraithknight Magnetization Tutorial | Modeling | TechWarPainting
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Understand the Methods of Magnetization and Demagnetization
Published: 2014/10/27
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9. Class 12 Physics | Magnetic Properties | Intensity of Magnetization | by Ashish Arora (GA)
9. Class 12 Physics | Magnetic Properties | Intensity of Magnetization | by Ashish Arora (GA)
Published: 2014/07/25
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221 Ansys Maxwell - Magnetization Direction [Modelling]
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Militarum Tempestus Taurox magnetization- Blue Table Painting
Militarum Tempestus Taurox magnetization- Blue Table Painting
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14. Physics | Magnetic Properties | Magnetization of Ferromagnetic Materials | by Ashish Arora
14. Physics | Magnetic Properties | Magnetization of Ferromagnetic Materials | by Ashish Arora
Published: 2012/10/10
Channel: Physics Galaxy
Demagnetizing and Cross magnetizing ampere turns
Demagnetizing and Cross magnetizing ampere turns
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Etheric body ( KA ) MAGNETIZATION
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Tau Tidewall Rampart - Magnetization
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Dropzone Commander - UCM Magnetization Guide - Part 1
Dropzone Commander - UCM Magnetization Guide - Part 1
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How Subwoofers Get Magnetized -  600v DC ZAP!
How Subwoofers Get Magnetized - 600v DC ZAP!
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How to magnetize metal
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Wilco - Magnetized
Wilco - Magnetized
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Miniature Painting 101: Part 49 - Basics of Magnetizing Miniatures
Miniature Painting 101: Part 49 - Basics of Magnetizing Miniatures
Published: 2015/02/23
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WIKIPEDIA ARTICLE

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In classical electromagnetism, magnetization (magnetisation in British English) or magnetic polarization is the vector field that expresses the density of permanent or induced magnetic dipole moments in a magnetic material. The origin of the magnetic moments responsible for magnetization can be either microscopic electric currents resulting from the motion of electrons in atoms, or the spin of the electrons or the nuclei. Net magnetization results from the response of a material to an external magnetic field, together with any unbalanced magnetic dipole moments that may be inherent in the material itself; for example, in ferromagnets. Magnetization is not always uniform within a body, but rather varies between different points. Magnetization also describes how a material responds to an applied magnetic field as well as the way the material changes the magnetic field, and can be used to calculate the forces that result from those interactions. It can be compared to electric polarization, which is the measure of the corresponding response of a material to an electric field in electrostatics. Physicists and engineers usually define magnetization as the quantity of magnetic moment per unit volume.[1] It is represented by a pseudovector M.

Definition[edit]

The magnetization field or M-field can be defined according to the following equation:

Where dm is the elementary magnetic moment and dV is the volume element; in other words, the M-field is the distribution of magnetic moments in the region or manifold concerned. This is better illustrated through the following relation:

where m is an ordinary magnetic moment and the triple integral denotes integration over a volume. This makes the M-field completely analogous to the electric polarisation field, or P-field, used to determine the electric dipole moment p generated by a similar region or manifold with such a polarization:

Where dp is the elementary electric dipole moment.

Those definitions of P and M as a "moments per unit volume" are widely adopted, though in some cases they can lead to ambiguities and paradoxes.[1]

The M-field is measured in amperes per meter (A/m) in SI units.[2]

Physics application[edit]

The magnetization is often not listed as a material parameter for commercially available ferromagnets. Instead the parameter that is listed is residual flux density, denoted . Physicists often need the magnetization to calculate the moment of a ferromagnet. To calculate the dipole moment m (A⋅m2) using the formula:

,

we have that

,

thus

,

where:

  • is the residual flux density, expressed in teslas (T).
  • is the volume (m3) of the magnet.
  • H/m is the permeability of vacuum.[3]

Magnetization in Maxwell's equations[edit]

The behavior of magnetic fields (B, H), electric fields (E, D), charge density (ρ), and current density (J) is described by Maxwell's equations. The role of the magnetization is described below.

Relations between B, H, and M[edit]

The magnetization defines the auxiliary magnetic field H as

(SI units)
(Gaussian units)

which is convenient for various calculations. The vacuum permeability μ0 is, by definition, ×10−7 V·s/(A·m).

A relation between M and H exists in many materials. In diamagnets and paramagnets, the relation is usually linear:

where χm is called the volume magnetic susceptibility.

In ferromagnets there is no one-to-one correspondence between M and H because of Magnetic hysteresis.

Magnetization current[edit]

The magnetization M makes a contribution to the current density J, known as the magnetization current.[4]

and for the bound surface current:

so that the total current density that enters Maxwell's equations is given by

where Jf is the electric current density of free charges (also called the free current), the second term is the contribution from the magnetization, and the last term is related to the electric polarization P.

Magnetostatics[edit]

In the absence of free electric currents and time-dependent effects, Maxwell's equations describing the magnetic quantities reduce to

These equations can be solved in analogy with electrostatic problems where

In this sense −∇⋅M plays the role of a fictitious "magnetic charge density" analogous to the electric charge density ρ; (see also demagnetizing field).

It is important to note that there is no such thing as a "magnetic charge," but that issue was still debated through the whole 19th century. Other concepts, that went along with it, such as the auxiliary field H, also have no real physical meaning in their own right. However, they are convenient mathematical tools, and are therefore still used today for applications such as modeling the magnetic field of the Earth.

Magnetization dynamics[edit]

The time-dependent behavior of magnetization becomes important when considering nanoscale and nanosecond timescale magnetization. Rather than simply aligning with an applied field, the individual magnetic moments in a material begin to precess around the applied field and come into alignment through relaxation as energy is transferred into the lattice.

Reversal[edit]

Magnetization reversal, also known as switching, refers to the process that leads to a 180° (arc) re-orientation of the magnetization vector with respect to its initial direction, from one stable orientation to the opposite one. Technologically, this is one of the most important processes in magnetism that is linked to the magnetic data storage process such as used in modern hard disk drives.[5] As it is known today, there are only a few possible ways to reverse the magnetization of a metallic magnet:

  1. an applied magnetic field[5]
  2. spin injection via a beam of particles with spin[5]
  3. magnetization reversal by circularly polarized light;[6] i.e., incident electromagnetic radiation that is circularly polarized

Demagnetization[edit]

Demagnetization is the reduction or elimination of magnetization.[7] One way to do this is to heat the object above its Curie temperature, where thermal fluctuations have enough energy to overcome exchange interactions, the source of ferromagnetic order, and destroy that order. Another way is to pull it out of an electric coil with alternating current running through it, giving rise to fields that oppose the magnetization.[8]

One application of demagnetization is to eliminate unwanted magnetic fields. For example, magnetic fields can interfere with electronic devices such as cell phones or computers, and with machining by making cuttings cling to their parent.[8]

See also[edit]

The dictionary definition of magnetization at Wiktionary

References[edit]

  1. ^ a b C.A. Gonano; R.E. Zich; M. Mussetta (2015). "Definition for Polarization P and Magnetization M Fully Consistent with Maxwell's Equations" (PDF). Progress In Electromagnetics Research B. 64: 83–101. 
  2. ^ "Units for Magnetic Properties" (PDF). Lake Shore Cryotronics, Inc. Retrieved 2015-06-10. 
  3. ^ https://www.kjmagnetics.com/glossary.asp
  4. ^ A. Herczynski (2013). "Bound charges and currents" (PDF). American Journal of Physics. 81 (3): 202–205. Bibcode:2013AmJPh..81..202H. doi:10.1119/1.4773441. 
  5. ^ a b c Stohr, J.; Siegmann, H. C. (2006), Magnetism: From fundamentals to Nanoscale Dynamics, Springer-Verlag 
  6. ^ Stanciu, C. D.; et al. (2007), Physical Review Letters 99, 217204 
  7. ^ "Magnetic Component Engineering". Magnetic Component Engineering. Retrieved April 18, 2011. 
  8. ^ a b "Demagnetization". Introduction to Magnetic Particle Inspection. NDT Resource Center. Retrieved April 18, 2011. 

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