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Magnetic Fields in Matter

Chapter 6. Magnetic Fields in Matter. Department of Physics , ROCMA. Magnetization. Magnetization. Magnetization. Torques and Forces on Magnetic Dipoles. rotation. Magnetization. paramagnetism. random. External B field. Diamagnetism. Ferromagnetism. Magnetization.

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Magnetic Fields in Matter

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  1. Chapter 6 Magnetic Fields in Matter Department of Physics , ROCMA

  2. Magnetization

  3. Magnetization

  4. Magnetization Torques and Forces on Magnetic Dipoles rotation

  5. Magnetization paramagnetism random External B field Diamagnetism Ferromagnetism

  6. Magnetization Force on magnetic dipole Case of uniform field (B=constant): 0

  7. Magnetization Case of nonuniform field (B ≠ constant): y x Fringing field B I

  8. Magnetization z I y x

  9. Magnetization z I y x

  10. Magnetization + Electric dipole - N Magnetic dipole I S Gilbert model Ampere model

  11. Magnetization Effect of magnetic field on atomic orbits

  12. Magnetization only electric force add magnetic field

  13. Magnetization when B is turn on,the electron speeds up.

  14. Magnetization

  15. Bound Currents

  16. Bound Currents

  17. Bound Currents 0

  18. Bound Currents --Using Biot-Savart law

  19. Bound Currents Exp 1: Find the magnetic field at the center of a uniformly magnetized sphere.

  20. Bound Currents Exp 1:

  21. Bound Currents Exp 1: θ R

  22. Bound Currents Exp 1: b

  23. Bound Currents Find the magnetic field of point P.

  24. Bound Currents q2 q u q1 R

  25. Physical Interpretation of Bound Currents When the magnetization is uniform:

  26. Physical Interpretation of Bound Currents When the magnetization is nonuniform:

  27. The Auxiliary Field H

  28. The Auxiliary Field H Exp 2: A long copper rod of radius Rcarries a uniformly distributed (free) current I. Find H inside and outside the rod. • The Auxiliary Field H

  29. The Auxiliary Field H Exp 2:

  30. A Deceptive Parallel Ampere law in vacuum : Ampere law in magnetic materials : Whereas ,the divergence of is not, in general, zero.

  31. Boundary condition a

  32. Boundary condition

  33. Linear and Nonlinear Media 磁化率

  34. Linear and Nonlinear Media 磁導率

  35. Linear and Nonlinear Media For linear isotropic homogeneous media Electric Magnetic

  36. Linear and Nonlinear Media Exp 3: An infinite solenoid (n turns per unit length, current I) is filled with linear material of susceptibility χ m. Find the magnetic field inside the solenoid.

  37. Ferromagnetism Ferromagnetic Materials : Fe, Co, Ni, Gd, Dy domain domain wall The domains range from about 10-12 to 10-8m3in volume and contain 1017 to 1021 atoms.

  38. Ferromagnetism Ferromagnetic domains. (photo courtesy of R. W. DeBlois)

  39. Ferromagnetism Hysteresis loop saturation remanence b c a g d f e coercive

  40. Ferromagnetism Hysteresis loop hard soft

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