12 -14 b-diamagnetism

1. Pertemuan 12 - 14 FISIKA ZAT PADAT DIAMAGNETIK Iwan Sugihartono, M.Si Jurusan Fisika Fakultas Matematika dan Ilmu Pengetahuan Alam

3. Magnetization The presence (or absence) of a significant magnetic moment for atoms will govern how they respond to magnetic fields. © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

4. Magnetization The presence (or absence) of a significant magnetic moment for atoms will govern how they respond to magnetic fields. For those that possess a significant magnetic moment, the application of an external magnetic field will tend to align the atomic magnetic moments © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

5. Magnetization Magnetization is a vector related to the magnetic moment of a material In fact, the magnitude of the vector is the magnetic moment per unit volume © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

6. Magnetization The response of a material to the application of a magnetic field will depend on the level of magnetization that the material undergoes B 0 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

7. Magnetization B 0 The magnetic moments are of course themselves, B-Field sources and will generate magnetic Fields of their own that may either strengthen the overall field or weaken it © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

8. Magnetization The total magnetic field equals the external magnetic field, B 0 , and the magnetic field generated by the alignment (or in some cases, creation) of atomic magnetic moments © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

9. Magnetization The influence of an external field is often expressed in terms of the magnetic field shown above Magnetic Field Strength © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

10. Magnetization The total magnetic field can then be expressed as the sum of the field strength and magnetization vector with the free space permeability,  0 . © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

11. Magnetic Susceptibility and Permeability Magnetic Susceptibility The magnetic susceptibility relates the degree (and sense) of magnetization given an applied field strength. It is characteristic of the substance and it is very much temperature dependent. © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

12. Magnetic Susceptibility and Permeability The expression for the total magnetic field can be rewritten as where The magnetic permeability © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

13. If the magnetic permeability,  m exceeds the free space permeability,  0 , ( a positive magnetic susceptibility) the material in question will either be paramagnetic or ferromagnetic If  m is less than  0 , (negative magnetic susceptibility) the material is said to diamagnetic. © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

14. Paramagnetism Paramagnetic materials possess significant atomic magnetic moments, often due to unpaired valence electrons © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

15. Diamagnetism Diamagnetic materials possess little or no atomic magnetic moments. What magnetization they undergo is induced by the application of an external magnetic field. © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

16. Ferromagnetism Like paramagnetic materials, ferromagnetic substances possess significant magnetic moments. Unlike paramagnetic materials, they have a significant attraction to other magnetic materials Ferromagnetic materials have other interesting features © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

17. Ferromagnetism Unlike the atomic magnetic moments associated with paramagnetic substances, the moments in ferromagnetic materials have strong interactions with their nearest neighbor moments . © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

18. Ferromagnetism Unlike the atomic magnetic moments associated with paramagnetic substances, the moments in ferromagnetic materials have strong interactions with their nearest neighbor moments . This leads to a strong correlation between large groups of magnetic moments in ferromagnetic materials © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

19. Ferromagnetism Unlike the atomic magnetic moments associated with paramagnetic substances, the moments in ferromagnetic materials have strong interactions with their nearest neighbor moments . This leads to a strong correlation between large groups of magnetic moments in ferromagnetic materials These large groups are known as “domains” © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

20. B H Paramagnetic Ferromagnetic Comparing the response of the total magnetic field to the applied Field Strength The relation for the Ferromagnetic curve is non-linear © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11 B H

21. B H Paramagnetic Ferromagnetic Comparing the response of the total magnetic field to the applied Field Strength The relation for the Ferromagnetic curve is non-linear In addition, if you decrease H for the ferromagnetic sample, the B field will not decrease in the same way, it increased © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11 B H

22. Ferromagnetic Because of the domains, ferromagnetic substances will retain a permanent B-field after magnetization. © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11 B H

23. Ferromagnetic Because of the domains, ferromagnetic substances will retain a permanent B-field after magnetization. This property, where the response to magnetization depends on the previous magnetizations is called hysterisis © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11 B H

24. H The area underneath the curves indicate the work done by H in changing the magnetic field of the substance in question © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11 B H B

25. The figure above shows a hysterisis curve between the two saturation points of a particular ferromagnetic material The saturation point corresponds to the maximum magnetization that a material can achieve © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11 B H B Saturation Point Saturation Point

26. To reverse the process of magnetizing a ferromagnetic material, one would have to follow this hysterisis curve © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

27. Magnetization Temperature A little Thermodynamics © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

28. Magnetization Temperature Phase Diagram of Typical Ferromagnetic Material Ferromagnetic Paramagnetic © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

29. Magnetization Temperature Ferromagnetic Paramagnetic Curie Temperature © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

30. Diamagnetism Unlike Ferromagnetism and Paramagnetism, the atomic magnetic moments associated with Diamagnetic behavior are induced by the application of a magnetic field B 0 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

31. Diamagnetism Unlike Ferromagnetism and Paramagnetism, the atomic magnetic moments associated with Diamagnetic behavior are induced by the application of a magnetic field B 0 In addition, the orientation of the induced magnetic moment will be such that the moments will be repelled by the applied magnetic field © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11 N S

32. Diamagnetism Many materials that at sufficiently low temperatures become superconductors, become perfect diamagnets Meissner Effect © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15/03/11

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