MAGNETIC MATERIALS

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MAGNETIC MATERIALS

• Origin of Magnetism
• Types of Magnetism
• Hard and Soft Magnets

Magnetic Materials Fundamentals and Device
Applications Nicola Spaldin Cambridge
University Press, Cambridge (2003)
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BASICS
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Material in a Magnetic Field

• The response of a material to a Magnetic Field H
  is called Magnetic Induction B
• The relationship between B and H is a property
  of the material
• In some materials and in free space B is a
  linear function of H but in general it is much
  more complicated and sometimes it is not
  even single valued

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Type of Magnetism Susceptibility (?) Comment
Diamagnetism ? 10?5 All materials are diamagnetic
Superconductor(Perfect diamagnet) ? 1
Paramagnetism 10?3
Ferromagnetism 102 105

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ORIGIN OF MAGNETISM IN MATERIALS
A moving electric charge, macroscopically or
microscopically is responsible for Magnetism
Nuclear spin
Weak effect
Unpaired electrons required for net Magnetic
Moment
Spin of electrons
Origin of Magnetism
Orbital motion of electrons
This effect is
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• In the solid the outer orbitals of the atoms
  interact to form Energy bands ? the simple
  picture used for an atom has to be modified
• Teh

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Diamagnetic
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A pole of unit strength is one which exerts a
force of one d