From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

These PowerPoint color diagrams can only be used by instructors if the 3rd Edition has been adopted for his/her course. Permission is given to individuals who have purchased a copy of the third edition with CD-ROM Electronic Materials and Devices to use these slides in seminar, symposium and conference presentations provided that the book title, author and © McGraw-Hill are displayed under each diagram.

Fig 8.1

From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

Definition of a Magnetic Dipole Moment

A magnetic moment

From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

Magnetic Dipole Moment

nm IAuμ Current

Area circled by current

Unit vector normal to the surfaceMagnetic moment

Fig 8.3

From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

Magnetic moment behaves like a magnet

A magnetic dipole moment puts out a magnetic field just like bar magnet. The field B depends on µm.

Fig 8.8

From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

Magnetization and surface currents

The field B in the material inside the solenoid is due to the conduction current I through theWires and the magnetization current Im on the surface of the magnetized medium, or B = B0 + 0M

Fig 8.9

From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

Ampere’s circuital law

From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

Ampere’s Law and the Inductance of a Toroidal Coil

Ampere’s law

IdlHc

t

NI

HB roro

AN

I

NL ro

2

Current

dedflux threa Total

Magnetic field inside toroidal coil

Inductance of toroidal coil

Fig 8.15

From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

Ferromagnetic Materials

In a magnetized region of a ferromagnetic material such as iron all the magnetic momentsare spontaneously aligned in the same direction. There is a strong magnetization vector Meven in the absence of an applied field.

Fig 8.16

From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

Antiferromagnetic Materials

In this antiferromagnetic BCC crystal (Cr) the magnetic moment of the center atom iscancelled by the magnetic moments of the corner atoms (an eighth of the corner atombelongs to the unit cell).

Fig 8.17

From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

Ferrimagnetic Materials

Illustration of magnetic ordering in a ferrimagnetic crystal. All A-atoms have their spinsAligned in one direction an all B-atoms have their spins aligned in the opposite direction. AsThe magnetic moment of an A-atom is greater than that of a B-atom, there is net magnetization,M, in the crystal.

Fig 8.20

From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

The exchange integral as a function of r/rd, where r is the interatomic distance and rd the radiusof the d-orbit (or the average d-subshell radius. Cr to Ni are transition metals. For Gd, the x-axisis r/rf where rf is the radius of the f-orbit.

Fig 8.24

From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

Magnetocrystalline anisotropy in a single iron crystal. M vs. H depends on the crystal on thecrystal direction and is easiest along [100] and hardest along [111]

Fig 8.25

From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

In a Bloch wall the neighboring spin magnetic moments rotate gradually and it takes several hundredatomic spacings to rotate the magnetic moment by 180.

Fig 8.26

From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

Potential energy of a domain wall depends on the exchange and anisotropy energies

Fig 8.27

From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

Magnetostriction

Magnetostriction means that the iron crystal in a magnetic field along x, an easy direction,elongates along x but contracts in the transverse directions.

Fig 8.30

From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

Schematic illustration of magnetic domains in the grains of an unmagnetized polycrystallineiron sample. Very small grains have single domains.

Fig 8.32

From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

(a) A typical M vs. H hysterisis curve(b) The corresponding B vs. H hysterisis curve. The shaded area inside the hysterisis loopIs the energy loss per unit volume per cycle.

Fig 8.40

From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

A Single Domain Fine Particle

A single domain fine particle.

Fig 8.43

From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

(a) Point P represents the operating point of the magnet and determines the magneticfield inside and outside the magnet. (b) Energy density in the gap is proportional to (BH) and for a given geometry and size ofgap this is maximum at a particular magnetic field Bm* or Bg*.

Fig 8.58

From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

Giant Magnetoresistance (GMR)

A highly simplified view of the principle of the giant mangetoresistance effect.(a) The basic trilayer structure.(b) Antiparallel magnetic layers with high resistance RAP. (c) An external field aligns layers, parallel alignment has a lower resistance RP.

Fig 8.61

From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

The principle of longitudinal magnetic recording on a flexible medium, e.g. magnetic tape in an audio cassette